see linked post. I believe this would count as one of the examples given in the federation policy https://lemm.ee/post/401063 :
An instance which is knowingly spreading CSAM into the federated network
Hexbears. A lot of people call for you guys to get defederated, but have seen a few hexbears be genuinely nice and helpful. I’m sure you can see my point with that one
Put it to a vote. If they vote against us, then c’est la vie. My only stipulation is that we get a chance to present our case (as our opponents also would).