Definitely this. Blocking communities is the way to go for community problems. Defederation is for server-wide problems (like the management of bot swarms, which I hope to be a temporary issue and that re-federation will happen as soon as it is resolved)
Damn. I hadn’t actually seen the exploding-heads community, but I went over to read their rules (seems fine) and posts (yikes). I am surprised that their rules even say what they do, as most of the comments in most of the posts I read would be breaking them.