You mean libelous (written) not slanderous (spoken).
And you omitted an important adjective: allegedly
That is a matter between the allegedly libeled parties, the poster(s) and a court of competent jurisdiction. We are not arbiters of truth and do not assess what is true or false, and by extension what is or is not libelous. If and when a court finds certain content to be defamatory or otherwise actionable and issues a ruling and order to that effect, we would take such an order under advisement. It's worth nothing that under current law, US-based interactive computer services cannot be ordered to to remove defamatory content, though they can certainly do so if they wish.