Yes absolutely. They exercise editorial control even if they attempt to disguise it behind “algorithms”. Everything posted on Facebook should be treated as if it was a newspaper article, for all legal purposes.
They had something like $18 billion dollars in profit last year, you don't think they could afford to hire an army of moderators?
Meanwhile, what about mailing lists? "But those aren't (necessarily) public! What if we want to put our proceedings on a web site?" Well, luckily there's precedent for that, and the word you're looking for rather than "put" is "publish", and you can absolutely do that, but, naturally, it's publishing, just like if you were to publish a private physical mail mailing list.
Either physical publishing needs to get the same protections certain kinds of web publishing have now, or we need to rethink what we've done with web publishing. Unless there's reason to believe we don't need those laws around traditional publishing anymore, the latter seems like the better idea to me.