They’re probably stressed that someone’s going to make them be honest about their weight. I wouldn’t shop at a store that made me do that.
The total level of suffering must remain relatively constant. Thus, by taking steps to improve one’s physical health, the system must readjust other factors to keep the total level approximately constant. Thus, by removing a level on internal suffering, this burden must be spread to others, lest the equation does not balance. As seen here, the internal suffering caused by lack of nutrition and health becomes an external one of contempt for one’s fellow man for not taking care of themselves as well as you are. Thus, the somewhat larger individual suffering is spread thinly by means of rudeness over everyone else. Unfortunately, since most of these people tend to shop in the same place, a lot of the rudeness just get’s piled up on the very same people who have just eliminated the internal suffering, and thus you have essentially replaced the lack of physical health with additional emotional stress and contempt. This, in turn, continues of a vicious cycle of outdoing those for whom you feel contempt by becoming more physically healthy and then absorbing more rudeness and stress. This will at some point, likely in the near future, result in all shoppers at health food stores being in absolute perfect physical condition and positively the most stressed and contempt-filled individuals on the planet.
Or maybe it’s just the whole holier-than-thou thing someone mentioned up thread…
My best friend is a vegan, and is very bubbly.
I’m guessing you’ve never been to Louisiana. Or the rest of the South, for that matter.
I used to work at a health food store and don’t remember the customers as being particularly rude. There was one man once who just stood at the counter and demanded I fetch all his purchases for him even though it was a self-service shop. There was nothing wrong with him physically - seemed more like a twisted way of getting his kicks.
That’s not funny. Take her out of the broiler, now!
No, just repeating what my Midwestern mother told me.
Bubbly? Hm, yes, beans, cabbage and broccoli will do that to a person.
I’ve found that anyone who sets value-based behavioral boundaries (other than the basic thou shalt not kill, etc.) will inevitably end up being a pain in the ass to others because of it.
I’ve also found that people who work at do-gooder jobs are 99 times more likely to be assholes than people who work at politically incorrect jobs.
This is disconcerting, because I want to do good things, but damn if I don’t despise the weenie-ass company I have to keep to do it.
Okay, then order the baby monkey brains 
I’ve made this point before.
Committed activists, on either end of the political spectrum, tend towards being humorless, convinced of their own rectitude, and untouched by any trace of self-doubt. I view people like this as dangerous, as their is nothing they won’t countenance if they see it as being For The Greater Good. Such people tend to view the rest of humanity with, at best, disdain.
A lot of people who shop at natural food stores do so because they like the food, and think it is healthier than conventional supermarkets. But, there is a significant group who shop there because it is The Right Thing to do and No Decent Person Would Go Anywhere Else. These are probably the rude ones you have encountered.
You can see the same sort of attitude on the opposite end of the political spectrum. Just hang around a fundamentalist church. There are many who go there for the social interaction and because they find comfort in their faith. These people can be as pleasant as anyone else. And then you have the ones who are Just Plain Better Than You…
I view a sense of humor as a saving grace, as a person who can laugh at themselves must at least once in a while admit that they aren’t always perfect. People without humor scare me a bit.
Oh man, the River Oaks Whole Foods here in Houston is the absolute worst. Right down the street at Central Market, fine, just crowded. Yet for some reason, it’s nothing but the biggest assholes at Whole Foods, not even a mile away. I think it’s because it’s the richest part of Houston, so these rich people think the world revolves around them and don’t even give a shit that there are other people on this planet. No one will move out of the way, they will walk right into you, run over you with their carts, stand right in front of you, all while talking on their cell phones about nothing and wearing full faces of make-up and expensive pink yoga clothes. I hate them so much, which is why I never shop there. Other Whole Foods aren’t near as bad though. Just this one.
I don’t know if this happens at the healthful foods store, but from my experiences elsewhere, I can tell you that this is a thing.
As Bill Hicks put it, “I’d quit smoking if I wasn’t afraid of turning into one of you obnoxious, self-righteous assholes”.
A couple of months ago one of the talking heads on FOX (I think O’Rielly. He’s the older guy, right?) was saying something like this when I wandered into the room: A lot of people, in his opinion, think that caring about the environment absolves them from traditional morality, specifically caring about other human beings. Maybe he shops at natural food stores 
This is not confined to new age religions. Saying you feel goodwill toward the universe in general (or toward a god or gods) is easy. Actually behaving civilly to other humans, even when you’re tired and in a bad mood, is harder.
My grandmother used to get a lot of these health food magazines. And based on those there would appear to be a very strong correlation between being into health food and being generally anti-establishment with regards to any number of other issues. I’ll bet the percentage of health foodists who believe that vaccines cause autism is five times the average for other people, even though vaccines aren’t specifically related to health food. It’s a general attitude that the whole world is being led by the nose by evil people and only you and a few other clear thinking people see through it.
This type of attitude is correlated with a general bitterness at the world, which naturally spills over to everyone in it. Although it’s hard to separate cause from effect here.
In sum, what several other people have already said.
There must be a spectrum of people like that, then. I’ve recently met a bunch of people that are totally anti-establishment, crunchy, granola types, and they were quite possibly some of the nicest people I’ve met in my life.
Then again, most of them shop at TJ’s.
I suspect that this has more to do with what you personally find annoying than with anything else. My experience is that most people in general are equally annoying and rude but I tend to get more upset with some rather than others.
For example: In my day to day commute if I get cut off my a Prius or mid sized sedan type car I have a pretty moderate “good for you! You are now one whole car ahead and have pointlessly endangered me” attitude. Like I am annoyed but not really mad. Same thing happens with an SUV or like a BMW or Mercedes and I am quite a bit more pissed. This has nothing to do with the behavior of the other drivers (that is consistently horrible) and everything to do with my personal value set (Because I am a godless socialist lefty type). I don’t pretend that this is the Best Thing Ever™, but there you go.
Hey, my grandmother herself was a health food nut of the worst sort (& it got progressively worse as she got older) and she was one of the sweetest people around.
It’s just a tendency.
OTOH, she herself was not the anti-establishment variety of health food nut. Just a bad case of single-issue health nuttism.
(Did anyone ever try to substitute carob chips on you instead of chocolate chips? Yuck!)
Still she lived to her mid 90s, and lived at home with all her faculties intact until the end. So maybe it worked for her.