I don't think vegetarian is enough, since it often means diary, which goes back to cows as one of highest polluters.

Could be that one needs way fewer cows to produce diary equivalent to beef, that would invalidate above sentence. Anybody knows this?

I've lived for maybe 6 months in cca vegan diet when backpacking in India and Nepal (apart from infrequent paneer cheese, their meat in cheap dhabas was not great to be polite - either chicken bits chock full of bones or very chewy mutton), but I wouldn't consider it the best idea for everybody alive. Also those indian spices helped mentally to feel like eating great, but I know very few (specifically) men in Europe who would find it acceptable replacement (women seems more reasonable in this).