The key here, is that relays are the only ones that can truly moderate content for a community because they can hard-delete, block universally, allow universally, define allowed or blocked keywords, manually curate, etc.
Everyone else can only issue events and hope for the best, but a relay is a real server and directly controls the data set on a machine. That's much more persistent.

And communities need to determine what they trust, and what they don't. Then individuals can choose a community whose moderation they prefer, or run their own. Because to trust data, is to value its usefulness and accuracy, but valuations are always subjective.