I'm not vegan, and the posts aren't aimed at me. Just have a look at c/lemmyshitpost

They are a small, harmless minority. Isn't that enough? Maybe it's made worse by the fact that they are perceived as non-violent and effeminate, because of their strong opposition to suffering, even when the victims are helpless, like animals. There is no personal risk in bullying them. It's like the hate for environmental activists, trans-women, or liberals in general. I wouldn't know that vegans aggressively proselytize their life-style if people didn't aggressively tell me so; something that they share with "the gays". Of course, people wouldn't mind if they didn't shove it in their faces all the time. Where have I heard that before?

The vegan hate likely comes from people who dont really know vegans or only know them from the internet so they only know the vocal minority

There is a small vocal minority that essentially equates anyone who keeps eating meat regardless of circumstances, preference or nuance, [to killers, murderers, etc]. Honestly a large amount of people would take a vegan option if it tasted the same, had the same texture, was as cheap or cheaper than meat, was as accessible, and didn't require learning a new skill set. There's also the availability when eating out.

Antagonizing people like that is a good way to have them disagree out of spite, and the militant vegans always have a way of inserting themselves into every conversation. I had to block people on lemmy because I just didnt want to deal with that here.

Unfortunately a vegan who is a good person isn't alwayd out there proselytizing at every chance they get in a non intrusive manner, so people rarely if ever see vegans who are reasonable people relative to vegan extremists.