I agree, vegetarians and vegans who try to force their lifestyles on you are wrong, and annoying. However I feel this way about all kinds of stuff, like religion and opinions on various topics in general. It's your choice about what you eat, do, worship (or not), think, etc, but it's wrong when you act like your way is THE ONLY WAY and everyone else is wrong. It isn't wrong, just different. I happen to not eat most meat (quazi-vegetarian? what is it when you don't eat mammals?) because i don't like the taste, but I'm not going around telling my friends that they are horrible and unhealthy because they have a burger or a steak.
As for Greenpeace and PETA, their mission isn't bad but they totally go about it wrong. Supporting the environment is a good thing, burning farms growing GMOs because you don't like the idea of genetically modifying crops is one step above terrorism. Besides, do the PETA people realize when the dump paint on someone's mink coat that they will probably just buy another one, therefore killing more cute little rodents and weasels and totally defeating the purpose of saving the animals?