Attempts to moderate away the worst examples of it just result in people making variations that don't technically violate the rules.

The problem then becomes if the clearly defined rules aren't enough, then the people that run these sites need to start making individual judgment calls based on...well, their gut, really. And that creates a lot of issues if the site in question could be held accountable for making a poor call or overlooking something.

The threat of legal repercussions hanging over them is going to make them default to the most strict actions, and that's kind of a problem if there isn't a clear definition of what things need to be actioned against.