Oh no! Exactly the point I was not trying to make! The problem being everyone has had a runoff with the small proportion of non-civilized advocates, leading to fear / awkwardness / uncomfortable feeling with the majority of civilized participants. And the culture doesn't self police strongly enough to keep the non-civilized fraction under control.
No one wants to sit thru a lecture of "my self denial makes me superior" "I'm morally superior" "meat is murder" "hey wanna see some slaughterhouse pixs" "hey look at me this is my special snowflake reason" "I'm saving the planet, all by myself".
OPs question of why vegetarians are looked at like space aliens is because its impossible to predict if the next couple minutes are going to be agony or fun. Probably gonna be all right, but...
(edited to add, come on guys, cut it out with the world doesn't exist stuff, my very own sister pulled the "hey look at me this is my special snowflake reason" for a couple months when she was about 14... now stand by for a round of "well I'm not sure sisters exist in the real world, after all I only have brothers and my buddy is an only child so citation needed...")
(And slayed0 is a better writer than I am...)