"Imagine a world where we left idiots to say idiotic things, and didn't tie ourselves up in knots trying to protect the public from their ramblings."
The problem isn't that they "leave idiots to say idiotic things." They have given them a platform to distribute idiotic things, complete with an algorithm to direct those idiotic things to the people most receptive to them. Facebook is hardly "tying themselves up in knots trying to protect the public from the idiots' ramblings." They've only just now considered whether to stop helping them.
The proposed ban is not equivalent to stuffing a rag into someone's mouth because you don't like what they have to say. It's telling them that they can no longer use your PA system.
Personality, I think Facebook's whole PA system does not have benefits that outweigh its costs. I think the greater issue is that social media's model for distributing information creates incentives orthogonal to the validity of the information. If you think the issue should be resolved by correcting the system rather than trying to respond to every problematic consequence that emerges as a result, then I completely agree. However, don't act like Facebook can live and let live; they've created the environment where this happens solely for their own financial gain.