I have a friend that is mostly a vegetarian because he thinks a) the meat industry is often cruel. b) very destructive environmentally.

I'm okay with that. I don't eat veal or fish for the same reasons[1]. Veal is cruel. And fishing is horribly destructive. Where someone draws a line isn't as important as they do.

[1] Don't get me started though with Hippie Brahmans that won't eat chicken or beef but eat fish for 'heath reasons'