Manda Jo has it down perfectly. I work with about 20 people, two of whom I consider “friends” and to whom I can make wisecracks. The rest of them may be–I have no idea–religious or atheist; Democrat or Republican; wild-living free souls or taking care of ailing quadruplets. It’s my duty to get along with these people so we can work together quickly and painlessly; if I say or do something to make them dislike or avoid me, the workday gets all the more difficult.
Trying to accomplish a task as a team is just one of the hardest things. Group dynamics are massively fucked. People fall into roles and polarize and there’s no end to how dysfunctional and miserable things can get. Just read Lord of the Flies! The point of having a code of behaviour is that once everyone knows how to act they can cut out the emotional drama and confusion and likes and dislikes and blah blah blah and just think about what they’re doing.
It’s easy to see where to draw the line. You know it’s too casual when people are getting upset and work isn’t getting done (and there’s a boar’s head on a spike by the copier.) You know it’s too restrictive when everyone wishes they were dead.
There’s also the whole other fact that a lot of times you are competing for credibility and so any annoying trait you can hide, you actually want to hide it because it will make you more appealing in general and you would like a raise. Other times you work very well with someone you can’t personally stand. I am a very good team with a guy I really hate but we can work together because we keep our opinions to ourselves. I’d really like to stab him in the eye a lot. I think we’ve done some pretty cool stuff together and professionalism is what makes that possible. Sometimes you give one thing up to get another thing. That’s just how life works.
Does he know your screen name is Pokey?
Yet another thread where every reply I start to compose in my head is then put into words by DianaG – but, usually, better than I would have put it. I suppose I should thank her for saving me the typing time. 
People who say they’re “blunt” are usually just abusive and mean. In my experience, every single person who has complained about people being angry at them for being “blunt” is either self-deluded or a liar, and in actual fact they’re abusive assholes who deserve whatever they get.
People who are genuinely blunt and honest without being abusive never get complained about. They’re usually the most popular people around.
Which are you?
Here’s part of the reason: We have codes of behaviour in the workplace because people can’t choose their co-workers. Fart with your friends if you want - either you won’t have any friends soon, or you’ve found friends who don’t mind farts. But you’re all friends because you want to hang out together.
But in the workplace, I have no choice. I’m not there to socialize, I’m there to get a job done. Maintaining a professional attitude creates an atmosphere where people with nothing in common can get along and get things done. If I don’t like heavy metal, I sure don’t want to listen to yours. If I’m a religious person, I may not want to stare at the nekkid titties in your cubicle. I don’t want to smell your food and watch you eat it, and I most especially don’t want to hear about your sex life. The minute you start imposing your personal preferences on other people, you crowd their space and make it harder for them to get their own jobs done. Or let me ask you this: How would you like it if that highly religious person in the next cube started proselytizing to you, and prayed over you every time you swore? It would get on your nerves I imagine, no? Professional conduct is what saves you from that. Have the courtesy to reciprocate.
And there are no hard and fast rules - some industries tend to attract a certain kind of person, and their evolved codes of behaviour show it. For example, it’s pretty rare to find a formal dress code in a software development shop. And you’ll see lots of figurines of dragons and such adorning cubicles. It’s an atmosphere that makes the type of people who work there comfortable, and a manager who stepped in and demanded that they all wear three piece suits and patent leather shoes would have a mutiny on his hands.
Likewise, don’t try to show up to your first day as a lawyer in flip-flops and a ‘hang loose’ T-shirt. They have their own culture, and if you want to be a lawyer, you have to accept that.
Am I one of the few guys on earth who don’t find farting for farting’s sake to be hillarious? Sometimes it is funny, when coupled with an adverse reaction by an entire roomful of people, but generally it gets a “meh” from me.
That being said, I’ll go hide behind that couch in the corner.
You’re an adult. Adults don’t do those things in the company of other adults in workplace situations. Kids do them because they’re kids - if you don’t want to be thought of as “the kid”, then don’t do the above during work.
Do note, however, that workplaces may vary and some of the things you mentioned (like wearing jeans) will be considered OK in some environments and not in others.
However, I cannot imagine a scenario where anybody in authority would just “talk about sex” w/o asking for serious career damage.
Manda JO and Sam Stone have said it all. You two should get together and write a book.
I once had a boss who was blunt and aggressive. She let you know when you had made a mistake. Well, no, really she was embarrassingly, horrifyingly unprofessional and abusive. She would take people into her office and scream at them for 10 minutes, and everyone–co-workers and customers alike–could hear every word. People either left, or stayed despite her abuse because of other perks. I’m sure she drove customers away. She owned the place, or else she would have been fired from any other job. Almost everything she did–not just the screaming–has served me as a great template of how not to act at work.
And there is the liability issue. Talk at sex at work, hang Maxim in your cube, listen to sexist or violent heavy metal and when someone complains about the “sexual harrassment” and pervasive abuse they feel in the office…
But the truth is - its about suppy and demand. In 1998, with the job market tight, I hired some people I wouldn’t have normally hired. They were the first let go when we didn’t need them, and some of them have never gotten paid as much again. You can be a great Oracle DBA, but if I have a choice of two Oracle DBAs - one who is professional, and one who thinks its appropriate to talk about his sex life at work, guess which one I’m hiring.
Life is unfair, kiddo. Get over it.
And here are the facts about the McDonalds coffee case.
Sam Stone pretty much nailed it, but here’s a bit of additional perspective.
The school of sociological thought I studied in college is called “Symbolic Interactionism.” The central thesis is, more or less, that we’re all constantly in the process of acting roles for the audience of others (or of ourselves).
The next time you wait for a bus, take a moment to consider your own behavior – do you sit on the bench? If there is no bench, what behaviors do you exhibit that give observers a clue as to your reason for being there. Do you check your watch? Look down the street? Etc.
The way we behave tells others who we are. In any group of people, there is a norm – a set of behaviors, including verbal and dress cues – that members of a group recognize. Those who exhibit behaviors close to that norm are more likely to be accepted by the group and recognized as members of it by those outsiders familiar with it. Thus, dressing in a suit and tie will tend to get you recognized by most members of American society as the kind of person who wears a suit – some form of professional, or perhaps a missionary, depending on context. 
This is not to say that all norms are good, or that you have to conform. It is, however, the reason why “being professional” is important in a workplace – the set of behaviors described in the OP are not in line with the norm, and will generate friction.
Because doing most of that stuff makes you look like an enormous tool. No one wants to be reminded that they’re spending 40+ hours a week with an enormous tool.
Because in school, you’re not competing with other students to have the teachers give you assignments.
In business, being able to get the job done is the second half of the work. The first half is convincing people that you’re worth risking their money and time on by entrusting you with the project.
Remember, when a teacher gives you an assignment and you fail, the teacher doesn’t lose anything. They’re under no pressure to choose the right person to do the project; just the opposite, they’re supposed to give everyone the same chance. They aren’t spending money on your work, aren’t trying to use your work in the real world, and won’t face getting canned by an angry boss because their work isn’t finished, because a vital part (the one they hired you to do) wasn’t done properly.
Which brings us to professionalism. If I’m under pressure to hire someone to complete a project for me, why should I choose to give you my business? Because you get the job done? I don’t know that. I’ve never worked with you before, I’ve never met you before, I know nothing about you beyond what I see right here in front of me. If you want me to take the risk of entrusting you with something that could affect my career, then you either need to show me an impressive portfolio of past accomplishments (i.e., proving you can do the job), or you need to convince me that you’re not only smart, serious, hard-working and reliable, but that your smarter, more serious, harder-working and more reliable than any of the other people available to do the same job. For that, I have to make an assessment based on what I see before me, and looking sloppy, rude and distracted isn’t going to cut it.
Professionalism is a combination of doing the part and looking the part. Once the customer knows you and trusts your work, ‘doing’ should start outweighing ‘looking’. For first impressions, however, the opposite will be true. And for most businesses, there will always be first impressions to be made.
Just to clarify, in my post I’m not talking about getting hired to work in a company, I’m talking about your company (via you) getting hired by a client or customer to perform a job.
We aren’t talking about what people do outside of the workplace.
Tense is not the same as serious or professional. If I am spending a lot of money at a company, it’s because I have a serious need and I expect them to treat me seriously and professionally. If I see a bunch of jokers clowning around, I might suspect they will treat my project the same way. They may not but how do I know?
I’m 33 years old and have worked in a wide variety of companies. When I work at a company where I see a lot of people with toys on their desk, where excessive alchohol consumption is encouraged at company functions, where coworkers routinely hook up, where chronic lateness or long lunches are ignored or excused, and where the staff spends half their time making Simpsons and Family Guy quotes, my impression of that company is that isn’t a place to have a serious career. That is a place that churn and burns through 20-somethings and caters to a post-college juvenile mindset in order to keep them for 18-24 months until a new batch arrives. I don’t need my workplace to be “fun”. I need it to be an environment that will stay competetive so we all don’t lose our jobs in a year.
My current workplace has all manner of unprofessional behavior and it does affect performance. People showing up late and hungover because they were out drinking the night before. People taking three hour lunches because they think it’s ok. Constant inappropriate comments and behavior. And it’s not like it’s making people stay. Our turnover has been huge. Anyone who can leave does leave to be replaced by a barely trained kid in his first professional job. Don’t tell me that’s good for business.
I work in a professional environment, but there are exceptions made. I work at a newspaper; the reporters wear business casual and everyone else has to wear business attire. I, on the other hand, wear (clean and unwrinkled and the proper size) jeans, clean T-shirts and tank tops, usually with a button-down shirt over it, and clean tennis shoes or sandals.
I write obituaries. I don’t enteract with the public in person very often - usually it happens on the phone. However, when I am interacting with the public, face-to-face, they’ve just lost someone very close to them, and I and my company do not want them feeling like they’re dealing with a funeral director - we want them to feel like they’re dealing with someone JUST LIKE THEM, who sympathises with their situation, and hates having to tell them that if they want an obituary that talks about how wonderful the person was they’ll have to pay for ad space, but if they’d like a death notice that’s free. I’m the only one in the building allowed and even encouraged to wear casual clothing, so long as it’s inoffensive.
However, that’s unusual. The business world is professional for a reason, most of which have been listed above. Regardless of whether you think someone should judge you on your appearance and actions, they will. It’s human nature, so I suggest dealing with it. An example that jumps to mind - you see a gorgeous woman walking down the side walk in a low-necked halter top that shows her cleavage off to an advantage and a miniskirt that almost shows her panties. Most people are going to assume this girl is a slut. She may not be one, but she certainly looks the part. You may not be a bum, but you certainly look the part. See where I’m going with this?
That said, I find it inappropriate to discuss your sex life or someone else’s sex life at work. Or really, to talk about anything un-work-related except for at break times. You’re on THEIR time, not YOUR time. So long as they’re paying you, you should be doing what they say (within reason). Sex in any form does not belong in the workplace, unless, of course, you work at a whorehouse.
~Tasha
This is really hitting me. The formulation is really interesting.
At my workplace, professional is the norm, but a good deal of slipping away from the norm is allowed and even slightly encouraged, such as dark humor. This is because of two main reasons: 1) the people we work on can’t hear us, and 2) there is a continual quiet stress in working with the dead and with the aftermath of violence. I should add 3), most of the time we are working as a small group of about ten people who get to know eachother well. Not friends, we work together instead of socializing together; but we are very familiar with one another, so some slippage away from the “norms” is easy to allow, because we don’t need the behaviors to tell one another that we will comply with the rules. Fellow doc#1 can wear blouses that show off her impressive cleavage without anyone’s doubting that she is top notch at analyzing and autopsying a multiple gunshot wound homicide victim. I can make snarky humor comments to my colleagues without anyone doubting that I know how to be appropriately serious with the parents of a dead baby.
In situations like ours, which include police, nurses and docs in big city ERs, ICU staff, etc., you have to maintain “professional” as the norm so other people know what to expect of you, but some slipping away from the norm is allowed when it’s just us chickens. Which, to me, makes the slipping away more fun; it’s like stolen kisses, more intriguing than married kisses.
However. When it comes time to interact with the public, all cleavage and snarky humor goes away. We revert to professional norms. And, as Brainiac4 says, we use specific clues to let people know we will maintain professional norms. For me, the biggest clue is my white coat. I have a white coat thrown over the back of a chair that I may not wear week in week out, because I don’t need to prove to the ten of us that I am a doctor, and because it isn’t part of my self-image. But when I go to court, I bring the white coat, because there it identifies me as a specific chesspiece out of the set (or, if you will, a specific D&D player out of the role-playing set). And when our CSI guy tells me I have a distraught family in the waiting room who needs to talk to me about a dead loved one, out comes the white coat. Because the white coat says: I will adhere to certain professional norms. I will tell you the truth, although I will do so gently. I will not use the truth against you for personal gain. I will be kind to your emotions, but keep you at a little distance. If you get angry at me, I will not retaliate. And so forth and so on.
And I do find that the white coat makes families relax and have an easier time hearing me answer their questions.
Maybe one family in a hundred would relax better if I came down the hall in t-shirt and jeans, but I have no way of knowing if a given set of strangers comes from that family. So I use the cues that state that I will adhere to my professional role for the families in their time of need.
Quoting OP:
How does the following interfere with performance?
*Gum chewing
*Cursing
*Wearing jeans and t-shirts
*Listening to heavy metal or rap, instead of elevator music
*Talking about sex
*Eating during meetings
*Having pages ripped from Maxim taped on your cubicle or office walls
*Having a GI Joe or Tweety Bird collection
Some of these may depend on individual situations or what type of workplace it is.
That said, I teach college classes. For my part, I cannot chew gum because it would interfere with the teaching/speaking.
I don’t curse because cursing in that room would probably get me into trouble if someone made a complaint, and it’s not necessary anyway.
I can wear jeans and t-shirts if they’re decent-looking.
The music factor is a non-issue, as is the sex talk.
Faculty and staff have been known to eat quite a bit during meetings, especially during the lunch hour, but it’s the whole group, not just one person chowing down. We do not eat in the classroom; see below.
Maxim pages = not a good idea due to sexual harassment policies.
Collections: Wouldn’t fit in a cubicle. Might fit in a faculty member’s private office if they could actually find room for it.
As for the students:
They do chew gum but I tell them not to pop it. Popping is rude and a distraction.
They don’t swear and talk about sex while in the classroom. I’ve got them too busy doing their work.
Students wear darn near anything.
I tell students to turn off their music headphones and cell phones while in the classroom. Again, this is about rudeness and distraction. There is a time and place for listening to music of any kind. If it were a music class instead of a writing class, things would be different.
Eating in the classroom is not allowed. Why? It attracts rodents and insects, and creates even more work for the overworked custodial staff. Also, it is not a dining room. Students can eat all they want during breaks, outside.
Maxim and collections: not an issue in a classroom.
So, some of this has to do with context, with what is necessary, with the appropriate place and time, with the current laws and policies. Some of it is based on sheer practicality.
It’s like Chris Rock says. You might not be a ho, but you’re wearing a ho’s uniform.