This is all easy to say for non-trans folk who aren't being targeted for the next genocide. If we allow users like this to hide behind crypto-fascist rhetoric, vulnerable minority communities will be overwhelmed and pushed out by the sheer volume of hatred.

I am completely unfamiliar with federation as a concept so there may not be a way to effectively moderate an entire instance consisting of several communities, but if there is a way to protect vulnerable communities without de-federaring, it needs to be done.

They are not so easy to find. You'll need to be very familiar with modern bigot / authoritarian dogwhistles. Obvious things like slurs or calls for the death of an entire group are damaging, but far more damaging are the sneaky smart ones who say things like "Are you disagreeing with statistical facts?" or "You're delusional if you think there's any significant hatred towards [targeted_group]".

Community-voted rules are a nice idea, but you need to have at least veto power, as bad actors may propose and vote-brigade intentionally exploitable rules or rules that marginalize vulnerable communities.

Use your best judgment to protect your community against those who desire bringing hatred and abuse. Just be prepared to explain the reasoning behind your decisions, and be prepared for vote-brigading (however unlikely it may be) when you veto.