I'll repeat a few things I've been saying about this. To keep it ~~short:~~ less verbose:
What people call "toxicity" online relies heavily on irrationality, from the aggressor and/or the target. And politics raises the stakes of everything, so irrationality + political engagement is specially prone to generate catty behaviour, name calling, uncalled combativeness, and all that crap.
Now look at social media. You'll see irrationals infesting every platform. Reddit in special encourages it, and most lemmings are from Reddit.
Why this matters: because I believe people here are focusing too much on .ml and Hexbear, without noticing the problem would still persist without them.
Do you have some good examples of that? The more, the merrier - it might help people to get ideas.