"Do you have any food limitations?"
"Yes, I'm a vegetarianian. I only eat things that eat vegetables. So please clean your grill if you have ever used it to cook corn, asparagus, or any other disgusting non-food substances."
A variant of the “Vegan” species they actually tend to be rather respectful from my experiences, and are much less insufferable than the extreme “Vegans”
Friend:”Hey I’m going out for a burger, would you like one”
Vegetarian friend:”No thanks, I’m a VEGETARIAN. but you can eat whatever you want, it’s just your lifestyle choice.”
Friend:”That’s cool.”