I think what you're missing is that FB does employ an army of content moderators to decide if something passes their bar or not. And these are low wage, button clicking jobs along the lines of the AWS mechanical turk where without very explicit clear guidelines, you fall flat on your face.

For context, reviewers apparently typically spend ~0-3 seconds to determine if a piece of content (mostly pictures) is acceptable. Given the pace of content creation, I'm amazed they even get that long, I assume algorithms do a lot of the heavy lifting as well.

Even if you have extremely smart reviewers, if your guidelines aren't clear and you leave it to the reviewer's interpretation, you'd likely get extremely inconsistent results and that feels like a worse product experience than having no moderation at all.

So either have the govt decide these guidelines (esp. on political speech) and let them eat humblepie or let the platform do it and don't complain when they ban the POTUS.