Because I eat meat selectively, I welcome seeing vegetarian offerings on a menu. I don't think its rude at all for a vegetarian not to eat meat at a restaurant. Its like not being able to eat pork, seafood, peanuts or dairy products and a good restaurant will make amends for your requests, anyway.

It is rude for a vegetarian to bitch at a waiter for not having enough gluten-free bread to go around, but a true diner would know what restaurants to suggest instead of the ol'steer steakhouse. Sitting on the other side of the table from you carnivores, I am often stuck picking at an $8 caesar salad that was made four hours ago and I think its rude of you to be thinking the way you are.