If 50, 75, or 90% of users on an instance block a community, would that hinder moderation to catch instances of misinformation that did pop up? (I'm just asking as some have raised that as a concern, and I don't know if that's legitimate or not)
Here's a test somebody performed on Reddit. While not 100% the same mechanics, it illustrates how lack of opposition affects how a post is perceived.
The problem isn't about moderation, the problem is with moving the Overton window, as neutral parties start seeing a lack of viewpoints from one side of the discussion, and viewpoints from the other side getting upvoted and significantly more visibility.