It is a private entity causing harm to society by facilitating the dissemination of lies and hate speech.

The point is that this should be regulated and/or disallowed, much in the same way that you (fortunately) can't go on TV to call for violence against specific groups of people or to run false advertising, or, in a developed/civilized country, you'll be facing consequences.

One way of doing this would be for FB and other media to be forced to provide authorities with official (and validated) company information regarding the entities that are using their service for this end, much in the same way as would happen to a company running false advertisements on TV.