Defederation should be the LAST and FINAL option. From what I understand, this is a small instance that isn't causing much trouble outside of their instance. Block them on your own! I'm on lemmy.world, but personally I would like to keep up to date on the shit they post. I don't think we should start going around defederating communities that we disagree with, even though their opinions are shit, vile, offensive, and disgusting. Leave it up and block them on your own.
Edit: 10 years ago I used to be one of those intolerable fucks. Yes - exactly like them. Until I talked to other people on Reddit, real life, and listened to other ideas. I had a change of heart and hope even a couple of them could too. It happens.