They decided against paternalistic meddling and let discourse happen naturally? That sounds best to me. I don't want Facebook to be a school teacher hovering over a lunch table to make sure nobody swears. People posting "divisive" content is far preferable to the alternative.
Even disregarding anything but mental and physical health, the consequences are significant and quite real.
No, they don't need to become the gatekeeper of all "bad things"(tm) the same way they protect us from accidentally gazing at a terrifying nipple, that would be preposterous, but they could probably try a little harder to not act completely opposite to their users best interest as often as they do.
Especially when that happens to be a significant fraction of all the people on earth, that's probably not too big of an ask?