I have never see anything worth the hate.
You just have a very high tolerance for jackassery. You've seen plenty of evidence of hexbear hostility, i.e. the "dunk tank" that would justify not wanting to interact with hexbear users and have actively chosen to disregard it.
This is because you're kind of a jackass. Disregarding people engaging in good faith with "just trust me bro" is exactly the kind of thing people really hate hexbear users for. Not because of illegal activity or moral failing, but because they're assholes. While you may think this isn't worth de-federation, unfortunately moderators aren't some kind of legal authority, and if federating with hexbear means instance admins or community moderators need to put in triple the work to prune all the arguments and """shitposting""" hexbear users love, nobody is legally or morally required to put up with it.
It's legitimately that simple. Hexbear users are jerks and nobody wants to hang out with them, and that's enough to ban them from any given community or instance.