Humanity evolved eating meat. Even different races have varied digestive systems based upon diet. To simply forsake a vast chunk of your dietary evolutionary history seems somewhat shallow to me ... but then again, obviously, I'm not vegetarian. But that being said, I eat far less meat than most people who, like me, don't give a damn for the animals.
As an adult white male in my 30s, I am well beyond any kind of biological need for eating meat (I don't have the demands for appropriate proteins that a growing child's brain has, for example).
I have to agree with Ickorus' tongue-in-cheek response. Anecdotally, and through my own experience, almost every single vegan/vegetarian from a culture that is not typically vegetarian (ie non-Buddhist, for example) is .. well .. likely to skew towards the 'pretentious' end of the spectrum.
Don't get me wrong, I'm very arrogant. My nickname in one of my prior workplaces was 'Pretentio' (a nickname I came up with myself actually to describe my superiority issues). But someone who tells me they are against animal cruelty, yet wears leather shoes or belts, is a tool. Someone who tells me they think killing cows for meat is sick, yet has no problems squishing a cockroach underfoot, is a tool. It's all moral relativism, a flawed and, frankly, unscientific process.
I was vegetarian, actually, for a period of about 2 yrs. I'd just moved to university. New life, new surroundings. The girl I was interested in (who became my girlfriend and dare I say it almost wife!) was vegetarian. She said 'look, kissing a guy who eats meat makes me heave'. I could respect that. She also didn't like guys who smoked. So I stopped smoking.
As a curious side note, I found stopping smoking much easier than giving up meat. I felt lethargic, weak, and I actually *gained* weight (despite muscle mass reducing) during that period. Whether that is merely coincidence I don't know. I was also having a LOT MORE SEX ... that could explain the lack of sleep and preference for being in bed.
EDIT: I forgot to mention, I know nicotine is an appetite suppressant hence many people gaining weight when they stop smoking. But I'm talking over 2 yrs. Nicotine leaves your body in a matter of days.