Why do people avoid eating meat? Throwing aside the religious factor, their are a few reasons why people decide to go meat free.
Health Beliefs: This one has often been educated by another meat avoider. Or they read a book (or watched a video) and believed what they read. Remember belief can be very dangerous, do not trust anyone else's word, especially if they have something to sell. They'll spout off about "fat" being a killer and talk about ill health from the modern diet (lots of processed food) while pointing the finger at a natural product (meat). They'll rant on about the dangers of cholesterol and then look stumped when told that breast milk is incredibly high in cholesterol (it needs to be).
Moral Belief: Self-righteous and often condescending, they really think they are a better person than you and they want to tell you all about it. They often lecture on about animal cruelty, but sadly have no answer to the fact that trying to convince people to give up meat is human cruelty. They also get stumped when asked if they are allowed to eat tomatoes (which eat insects).
My motto is live and let live, I won't attempt to tell anyone what to eat, I even discuss it with my clients rather than lecture them. Do not trust a vegetarian who tells you they do it because it is healthier to avoid animal products and sources high in fat. A vegetarian. So yes, do eat more fruit and veg, but do not live on that purely in the belief that it will make you healthy.
Eat a variety of foods, get the best quality that you can, limit processed foods as much as is possible. Cook at home so you know what goes into it, and don't demonize food groups. Most of all, if someone disagrees with you, don't try to convert them. Save your energy (you'll need it if your on a restricted diet) and let them get on with it.
Final thought is that its slightly ironic that when veggies do crack its normally for bacon, which in my opinion is the worst meat you could possibly eat (aside from spam).