Why do meat eaters constantly preach to vegetarians?

I've never told someone I'm a vegetarian without being bombarded by questions. They start innocent enough - why are you a vegetarian and eventually turn into you're missing out on protein, God made animals for people to eat and the list goes on. On the other hand I never tell people not to eat meat though if asked I'll explain the benefits or state how harmful to the planet it is. So why do they feel they have a license to grill vegetables, I mean vegetarians?