I think vegetarians are justified in ASKING meat eaters to stop eating meat, as I believe they're entitled to formulate and defend their own opinions.
What I don't agree with is when "asking" becomes "telling", with some militant vegetarians thinking they're superior to meat-eaters just because they think they took the right decision when deciding not to eat meat. Everybody's entitled to their own opinion and their own way of life, and if you want to tell me about yours and try and convince me that meat-eating is wrong, fine, I'm okay with that. But if you're going to actually tell me what to do and tell me that what I'm doing is wrong without any arguments, I'm going to completely ignore you.