What strikes me as particularly weird is that I have a vegan friend who made a point of saying "I'm not going to tell someone else they shouldn't eat meat." I don't actually know what she meant by that - whether she honestly didn't think it was her business, or whether she simply had observed that telling people they shouldn't eat meat has the opposite intended effect - they get pissed at you for telling them what they should and shouldn't do, and either ignore you or eat more meat just to spite you.

If she meant the latter, I agree. I don't think I've ever gotten someone else to become Vegetarian, but the approach that seems to produce most.... "respect" I guess is when I:

a) Make an effort to point out that I will have a hard time eating at a particular restaurant or event because of few vegetarian options. I say this as matter-of-fact-ly as I can. When people go "wait what?" I say "yeah I'm vegetarian" without attaching any particular judgment to it.

b) when/if people ask "why," I focus almost entirely on reasons to cut back on meat that are [i]entirely in humanity's best interest.[/i] Most people are vaguely aware that there are "health reasons". And in fact, a lot of people say with hopeful looks "for health reasons, right?" because I don't sound judgy, and they have assumptions that the health-vegetarians are cool whereas the ethical-vegetarians are judgmental jerks. What people DON'T usually realize how bad the meat industry is for humanity as a whole (by way of the environment).

c) when I get to the ethical concerns, I focus specifically on factory farming. I'm not 100% sure how I feel about the absolute moral weight of animals who are killed humanely for food, but letting people feel like there's SOME way to ethically eat meat makes it feel less like I'm attacking them (even if that ethical way will almost never be relevant to the food that they'll have access to).

People SHOULDN'T need more reason than "animals are raised in cages, given growth hormones to the point where they can barely walk, left to sit in their own feces and then killed." But the magnitude of that reason is such that most people can't process it. So it's pretty convenient that there's plenty of other good reasons to help open people up to the idea.