I've honestly met more preachy meat-eaters than preachy vegetarians, though that could just be because I've been a vegetarian all my life so it was never a choice I had to make.
If I mention I'm a vegetarian, people often get this really weird, defensive look in their eyes and sometimes they'll start telling me that there's nothing wrong with eating meat. If they're really jerks, they'll start saying "For every animal you don't eat, I'm going to eat three!" I guess they must have had a lot of run-ins with preachy vegetarians and are getting preemptively defensive.
On topic, I just answered the question of why I personally am a vegetarian last night. Let me find my post and quote it.
"I was born and raised vegetarian. I was always free to start eating meat if I wanted to, but I was never interested. Partly for moral reasons (I don't feel personally capable of killing an animal, so I feel it would be hypocritical of me to eat an animal that someone else had killed), partly because I've never seen meat as "food," and partly out of sheer laziness. I don't care enough about it to learn how to cook it and to go through the long, uncomfortable process of getting my body used to digesting it."
Now let me add to it.
Yes, a vegetarian diet CAN be healthier than a meat-eating diet. You just need to be sure you're getting enough protein, iron, calcium, omega 3s, vitamin B12, and vitamin D, all of which you can get from non-meat sources. (I think that's everything; I just woke up and my brain is still fuzzy.) You can also get the same effect as a meat-eater by just reducing your consumption of unhealthy fat and eating white meat and fish more often than red meat. Different strokes.
For those people who say that humans were not made to be vegetarians, humans were also not made to take medicine. It's possible to remove meat from our diets by studying what it is that we get out of meat and then replacing it with other things without any negative side-effects. (Again, I'm NOT saying that this is what everyone should do. It's just an argument against people who say that being a vegetarian is unnatural.)
The other benefits have already been mentioned:
1. It's better for the environment. Yes it's true that some land is only suited to growing grass, but most cows in America are fed on corn, not grass.
2. It's much cheaper.
As for the drawbacks:
1. People who seem to think that I don't eat meat just so I can think I'm better than them, when I never said a thing about it.
2. It can be hard to find vegetarian options in restaurants, but I can always make do by either asking for a menu item without meat or requesting a grilled cheese sandwich or something.
Let me also add that I don't think eating meat is objectively wrong. Just wrong for me, because of the issues I mentioned about feeling personally unable to kill an animal. I also dislike the way animals are raised, and I'm much more supportive of small farms and hunting as far as obtaining meat goes, because the animal gets to have a fairly normal, happy life before being killed. Unfortunately those aren't very efficient ways to produce meat with the world in the state it's in, so I just don't eat meat at all.
(I do have a few issues with vegans, mainly the fact that they don't eat honey. Beekeepers and bees have a symbiotic relationship. The bees are just allowed to do what they would do normally, only they're provided with everything they need. They aren't being harmed like farm animals at all. But that's not important to the topic.)
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