Reddit’s AskHistorians subreddit – one of the largest history forums on the internet – doesn’t bother debating Holocaust deniers. Instead, it bans them, and one moderator says Facebook should, too, because “deniers need a public forum to spread their lies and to sow doubt among readers not well-informed about history. By convincing people that they might have a point or two, they open the door for further radicalization in pursuit of their ultimate goal.”