Interesting. All the years as a vegetarian I never "preached" at anyone about what they eat. I couldn't care less. I don't know any vegans and vegetarians that do preach at anyone. I have had issues with psycho meat eaters who get their panties all up in a knot about vegetarianism, though.
My favourite:
Meat eater: "Why don't you eat meat?"
Me: "Why don't you shoot up heroin?"
Meat eater: "I don't want that crap in my body."
Me: "Well then...?
Meat eater: (look of realization crosses their face)
I know a few that are very passive aggressive about it. The whole holier than thou attitude. Not everyone is like that, but there's plenty out there!