This is what it seems like every instance admin has not wanted to acknowledge: that tolerating the intolerant will destroy us.
Fortunately v0.19.4 has some new features that look like they may help - particularly the ability to label a community with a warning, like : "⚠️ You are about to enter the cesspit of human behavior that actively defends genocide (by mods removing all contrary facts), so long as it is done by the Right people (Russia, or ironically also Left, China)."
It's like the tiniest step that could possibly be done, and it leaves the ability for Lemmy.ml users to place comments in every post across the Fediverse too - unlike a bona fide instance block, although to my knowledge there are no major instances that actually defederates from them.