I've got nothing against being a vegetarian or vegan or out and out carnivore, but there are two things which irritate me:
1) When veggies force they're diets on their children (especially younger ones) and miss out on vital healthy things that they need. I see a lot of unhealthy pale vegetarian kids. I'm not saying it's a bad thing as long as you find replacements for the vitamins and stuff they don't get, but more often than not there are no replacements. We have evolved to eat meat - that is a fact.
2) When people insiste they are a "vegetaria who eats fish and chicken". That really annoys me.
I don't mean any offence to anyone, I think people are entitled to their own views, but it irks me when they try to force them on other people.