Are you saying that Facebook is a government? By the same token as libelslander, censorship is a government task. Everything else is just business rules.

No, it's not. Courts are a last resort, when private mediation has failed, not the first line of action. If I publish news articles claiming "the sky is the color red, and only evil people disagree", courts do not need to be involved for Facebook to bury my articles. Most mischief is obviously classifiable without outside mediation.

You think the New York Times doesn't decide whether something is libel or slander before they print it in order to avoid having the "courts...decide whether something is libel or slander"? It's not a direct comparison, but close enough for me to dismantle the idea that only courts get a say on this.