There are hate speech laws they can follow. That should cover the extremes. And if they don't, then it is the failure of the legislation.

Just like how you can't go to walmart and insult everyone you see. It would actually be illegal to retaliate against those people. But call the cops and they can be dealt with.

At least with the laws, there is more checks and balances. It isn't perfect, but it is better than giving private entities massive power to control opinions.