I see what you mean, I seem to encounter the militant veggie or even worse the vegan.
I love pointing out to those people that they really shouldn't be drinking wine or beer if they are that serious about vegetarianism.
Having worked in the catering industry chefs don't take kindly to vegetarians or those with "look at me allergies" aka i'm not really allergic but i like to make a fuss anyway.
My worst dinner party the guest list consisted of one lactose intolerant, one gluten intolerant, one with egg allergies, one with fish allergies and a vegan.

Funnily enough I had to cancel