There was a group of certain individuals who consider themselves Vegans who felt the need to tell everyone why their decision to not eat animal products is superior to those who eat meat.
I can think of a specific YouTuber who lives in an echochamber of Í know better." And there's quite a few who use their diet as a reason to feel superior. With the internet being the internet, that turns into a stereotype that gets reinforced by every time they see a Vegan who wants to explain their food choice.
Should never read comments, or rather, never respond no matter how much you want. It will only make things worse.
The internet is full of edgelords and "gotcha"comments. It's not worth the energy to participate in it, or to resent it. This is how people are. We vent on the interwebnets.
Vegans bashing is only one of many, many toxic behaviours.
But as much as we may have toxicity or unpleasantness around the subject, that doesn't mean it should be avoided.
EDIT: Welp, didn't know this was old until someone tried advertising on here :\
lul ignore me!