Fine, porn or gore or profanity, list of slurs. If you want to begin curating other nebulous concepts like "hate speech" at scale, it should be explicitly defined and you should held to being clear when you are acting upon violations for it, and responsible for applying your policy broadly and not cherry picking. "There is no neutral" so we'll just make it up as we go is just a ridiculous pass that big platforms are exploiting to the ill of society.
that's what we've always done, make it up as we go along, since societies and language change.
I doubt you'll find it easy to really split what's porn and what is art. or even what gore vs art is.