...into this garden comes a fool...Then another fool joins, and the two fools begin talking to each other, and at that point some of the old members, those with the highest standards and the best opportunities elsewhere, leave...
It reads to me like the fool is somehow intrinsically, immutably subhuman compared to the "knowledgeable and interested folk". It's as if we weren't all once not knowledgeable, as if the non-knowledgeable fool can never become knowledgeable. I'd say that compared to a disinterested fool, a non-knowledgeable fool who's interested and is attracted to this garden of "high quality speech" is easier to fix.
The conclusion seems to go against everything Less Wrong is about. It reads to me like, "biases? Nah, I bet nine times out of ten you're not biased at all. Downvote away!"