nah it’s just a reputation because people who make these choices usually try to spread the word, but sometimes it becomes perceived as obnoxious. vegans just got a bad reputation because it was relatively early internet days, i haven’t seen vegans being as obnoxious as weed smokers, for example.
now, weed smoking is objectively not a better lifestyle choice but i think they’re much much worse than vegans ever were. has nothing to do with arguing against things, not that I would argue against veganism anyway; i admire the choice.