I agree that this kind of content is disgusting. So the policy should be that it’s not allowed on this instance. It’s perfectly reasonable for you to not want this content directly on your server.

But, I don’t agree with defederation. I joined a general instance to be able to go wherever I want. It should be left up to me what content I don’t wish to see and simply block those communities myself. If you start deciding for me what I’m allowed to see or not see then I’ll leave to a different instance. Today it’s the obvious “no loli or child porn or w\e” and everyone hops on board because it’s easy to just not be a pedophile. But that opens the door to defederation in general. Tomorrow it could be something else.

Do what you will but make sure to state it publicly so I can know whether or not I should bother sticking around with this instance.