about 2 years ago, while in class, a classmate saw that I was drinking a regular coke and felt the need to tell me that it contained sugar, like it was a bad thing. I just looked at him and said “and…” had someone else tell me “I can’t believed you would eat that” refering to what I was eating at the time, cake at a party, beef jerkey… . I would look at them and tell them " yes I did, and it was good, and the people will rejoice bocause of it…"
I’m quite sure Miss Manners would not approve of the following, but I like it.
Regarding the bit in the OP, a good response is:
Or an alternative version:
Male stranger in grocery store, pointing to item in my mother’s shopping cart: “Don’t you know that stuff is not good for you? It contains yada yada yada—.”
My dear sweet gray-haired little old mom: “No, I didn’t know that. Thank you for telling me. Now, please go straight to hell and mind your own damn business on the way.”
Me: Laughing uncontrollably, consumed with glee and admiration.
being on the larger side of normal (6’4" 250lbs) I generally have 2 responses depending on the tone of the offender.
If said moron is polite, I usually look down at them and in as cranky a voice as possible reply “So?”
If he/she is an asshole, well I usually just threaten violence and it shuts them up.
On the off day that I just don’t give a shit, well sometimes I just play the silent game.
For those of you that don’t get to liten to Opie & Anthony (I know most of you don’t live in and around NYC) you sit there w/o speaking while smiling and nodding until the awkwardness just completely weirds them out into leaving. No not just leaving you alone but actually leaving your physical space. A truly lovely game but alas this isn’t the O & A message board so I shall end the hijack.
Where the hell do you guys shop for food? I have never in my life had a person in a grocery line say a word to me like these I am reading, regardless of what gastronomical atrocities are in my cart.
I read an item calle “Gossip” once, about the harmful effects of people talking about others behind their backs, about the ugliness of “rumors”, and other such nasty talk. Not precisely what is being talked about here, but the ending was quite appropriate for those who think they MUST tell a stanger something “for thier own good” Goes like this:
"Before you speak, ask yourself, ‘Is it true?’, ‘Is it fair?’, ‘Is it necessary?’ If it isn’t, SHUT UP!
Fenris,
Will you adopt me? 
I totally agree with you.
My husband used to make retching noises in the back of his throat whenever I was eating something he considered “unhealthy”. I used to tell him that, unless I was forcing him to eat the same thing at gunpoint, he needed to shut up. I’m glad we’re past that. I seem to have corrupted him; he eats junk now, too:D.
I hear you, man.
I don’t mind it at all when people do this. I actually like it, because I will not hold back. I will not keep my peace. I will very pointedly tell them what I think of their advice and what they can do with it. Usually I like to respond appropriately:
“Thanks for the tip. Who are you, my fuckin’ therapist? Take a walk!”
or
“If I wanted you to open your mouth I would have told you to suck my dick.”
or
“Look pal, you’re the last person I want to take (diet, fitness, financial, whatever) advice from.”
or
“This is an A and B conversation so why don’t you shut the fuck up?”
or
“Thanks. I have some advice for you: Why don’t you go outside and play a nice game of hide and go fuck yourself?”
Sometimes people start blurting out “You could lose weight if you…” and I hate that. I don’t really run into it, I don’t know why. No one has ever taken upon themselves to advise me of my eating habits. I usually hear this sort of stupid shit while hanging out friends, as people will tell them this sort of thing when we’re out at a restaurant. I don’t mind hopping right in and asking the “samaritan” things like:
“Uh-huh. Yeah, yeah, yeah. If, if, if. If my aunt had balls, she’d be my uncle. What’s with all the “if” shit?”
and
“I know. Too bad you can’t cure horse-faced buck-toothed pure-D ugly with diet and excercise.”
or
“You want me to use your ass for a bucket and your head for a mop? Tell your story walkin’, jackass.”
It’s great, because these people usually do not expect to meet this degree of hostility. They don’t expect that someone will get right in their face and tell them to take a flying fuck at a rolling doughnut.
Yes, I am a big fat flabby fried-chicken BBQ rib eatin’ motherfucker.
Yes, I’m okay with that.
Yes, I can kick your lily ass, Mary, so don’t ask. I have have seen chunks of balloon in dog shit that are bigger than you.
This is a little off-topic, but not completely. For awhile, I was madly in love with this guy who had no interest in dating me. He always gave me these terribly lame excuses until one day when I asked him to tell me the truth. He said he didn’t want to date me because I was ugly (“not conventionally attractive” was the exact quote). I was really upset for a long time, but I realize that I owe him something (and I kinda respect him) for telling me the truth. I’ve been dumped before, but usually with clearly fake excuses. Looking back on it, I’m glad someone was honest with me.
Of course, I did ask for the truth, so this doesn’t really apply to this topic.
I dunno - a line like that just rolls off the tongue.
I can’t help but love you, Lexicon.
My new favorite line? “Uh-huh. Yeah, yeah, yeah. If, if, if. If my aunt had balls, she’d be my uncle. What’s with all the “if” shit?” 
God. Glad I wasn’ there. I probably would’ve given myself a stroke laughing.
My mother used to bug my brother a lot about being too thin. She never really seemed to grasp that people who run 7-10 miles a day (like my brother) are naturally thin and quite healthy indeed.
The correct response is, of course, “If I’d wanted your opinion I’d have beat it out of you.”
The only bad flip side to this is when you actually do want to be brutally honest with someone because they’re headed for disaster, and they don’t hear you. But that’s not for strangers on a train…
Esprix
I was at a donut shop a few days ago and ordered four maple filled bars. The woman behind the counter goes, you’re going to eat all four of those? And I said some lame ass thing about not all at once. Of course I thought of many snappy combacks on the way home. Almost to the point of returning to “tell her off”. I then realized what the hell for. Who cares what some stranger thinks.
Lexicon not only did this actually make me smile tonight, but now I want to be a guy so I can use this line. I’ll probably use it anyway. This level of crude hostility makes my heart go pitter pat.
I had a rough childhood.
I must say, Medea, the effect would only be intensified when being sneered by a woman.
Seriously, if someone like Byzantine were to snarl and tell me this, I would tuck my tail, whimper, and run away.
This is a wonderful thread. I love all of you!
You all realize its just healthier for you to just let it go.
I’ve never used this - I just thought it up, but it might be worth a shot.
Interloper: Here’s some advice for you yadda yadda yadda…
You staring intently at Interloper’s face
Interloper: Why are you staring like that?
You: Your nose.
Interloper: My nose? What’s wrong with it?
You: It’s in my business.
Tip o’ the pint to LouisB’s mom too. Verbal suckerpunches are the best!
Something I always tell my (poor) husband or family whenever I get unwanted advice is the cold, stiff glare and “Your opinion has been duly noted.”
Torques 'em right off.