My personal experience has actually been quite whew opposite of everyone here apparently. Of the 3 vegans I’ve spent time with, not one of them has ever brought it up to preach or to sound smug. It only ever comes up because I ask for a recipe they served and they say something along the lines of “now, this is a vegan recipe, but you should be able to substitute ‘x’ with ‘y’ if you wanna avoid that.” It’s never preachy, it’s always in the “don’t let this being vegan ruin it for you” kind of way.
My low stakes conspiracy is that vegan hate on the internet is like people that don’t like the word moist. They either watched friends and decided to adopt that as a personality trait, or they look up to someone that did just that. They hate veganism because they watched a comedian quip about it and agreed or they saw someone that watched a comedian and agreed. It’s all too consistent to not be feeding from the same bowl.