It's worth pointing out that a lot of other countries on Earth have laws that prohibit hate speech. Quite a few countries have libel laws, too. The US does not have either of those at the federal level, making it much more difficult to use the law to stop people from inciting violence and spreading blatant lies.
It's true--I think--that there is no federal libel statute (though perhaps someone can correct me on this), but that assertion is misleading without a little more context. Whether it is a state or federal law doesn't really mean much in the American legal system. In the U.S., most such laws are state, not federal laws. That doesn't make them less important or enforceable.
Every state that I know of recognizes libel as a tort (i.e., you can sue someone for it), and you can do so in federal court if the required ents for federal jurisdiction are met. (In this case, probably that the plaintiff and defendant are from different states.) And, in any case, what's wrong with state courts? A judgement in a state court is just as good as one in federal court.
Well that in itself is a crime, so prosecute it.
Where did I indicate getting banned from a website was too far?
I liken it to having a toxic person in your life who can't admit that their actions are ever wrong - what do you do in a situation like that? At some point, you just have to cut them off.