I agree that vegetarians and ESPECIALLY vegans can get attacked. I've been a vegetarian for 14 years now and people (co-workers, relatives, family, etc.) still give me the third degree on it.
I was vegan for several months. I still don't drink cow's milk (yuck) and don't eat eggs (yuck) and the only non-vegan thing I can tolerate ibs-wise is yogurt. I add it to my granola for breakfst and it's yummy.
The main reason I couldn't be vegan is because there are no delicious cheese substitutes out there yet (I've tried dozens) so I ended up craving cheese (pizza, nachos, burritos) and caved in.
I think people that can be vegan have a lot of willpower and that's commendable. Also, they can get all the nutrients from plant dervived sources. The only thing they can't get from plants is b-12 but you can get fortified soy milk which if you drink 3 glasses a day gives you your daily requirement. (I saw a nutritionist about my requirements).