Facebook didn't just pop into existence as some magical technology or culture, it simply is a corporation that rides on top of infrastructure that it doesn't have any control over. Its only purpose is to take what one person says and show it to other people it thinks want to hear that message. It's not novel in any way, but it is a publisher and as such, should be beholden to the same rules of truth - and responsible for the messages it rebroadcasts.
It is not censorship when a party sues another party for libel. It's not censorship when promoters of genocide are tried for aiding and abetting genocide. You don't understand what censorship is.