They’re easy to hate - They’re weird, eat funny foods, care about things nobody else does (who cares about chickens) and my god is there a subset of them that are the most truly obnoxious human beings (a statement that is, conveniently, true of every single group of humans). They’re basically furries for the non-internet crowd. Nobody ever interacts with them to know it, so they get defined by the strawmen people create of them.

Edit: It’s possible my explanation of why vegans are disliked has touched a nerve. To clarify; I don’t think this, hell I eat vegan meals most of the time, but these are the qualities given to the Strawman Vegan that everyone onlines seems to love to hate. (I also quite like furries.)