Who decides when speech is free and when it's hateful?

Free speech. Facebook's Mark Zuckerberg says the platform won't ban holocaust deniers from their denying. "I'm Jewish," he says, "and there's a set of people who deny that the Holocaust happened. I find that deeply offensive. But I don't believe that our platform should take that down because I think there are things that different people get wrong. I don't think they're intentionally getting it wrong."