Vegetarian/Gluten Free/Low Carb diets

I mostly think that people should eat what they want to eat.  The problem with these artificially limited diets is that they are ALWAYS imposed on other people.  You don't want to serve me steak at your house?  Fine.  I'm happy to eat vegetables when I'm a dinner guest at your place.  But etiquette is not situational: the rules of being a dinner guest still apply when you're at my house.  Eat the goddamn steak. 

If you're on a low carb diet, don't eat the bread basket at the restaurant.  But don't explain to me why I shouldn't eat it, or tell me how much weight you've lost since you stopped eating bread.  Good for you and pass the butter, please: I don't want to hear about it.  Gluten free?  Whatever, don't order the pasta.  But don't make the server make special requests to the chef to leave the croutons out of your salad.  Hell is other people's artificial dietary restrictions.