Fairly early on, when discussing defederating with an instance called "exploding heads", I laid out criteria I would consider worthy of defederation, which you can find here
I was primarily concerned with unwanted traffic going out over the rest of the Fediverse, hosting illegal content like child porn, or being a rampant hive of racism and calls to violence.
So far I've basically heard people accuse Lemmy.ml of being rather Chinese in their moderation in-house. Is that all we've got?