Most of the rationality minded people I know, especially including myself, have a strong tendency to dispute the status quo, and disagree with authority just for the fun of it. So I imagine that if I came across LW in that setting, I would have criticized it in my blog comment just because it was non-conformist and required more original thinking.
I feel the same way. I think that intelligent people tend to do that because intelligent-sounding disagreement is more difficult than intelligent-sounding agreement, and thus a better way of signaling their intelligence to other smart people.
I would say it was the other way around. It's easy to be against something, and it sets you above whatever you're criticising. It's much more difficult to sound smart while agreeing with something.
I discount the smart-soundingness of whatever I read accordingly.
ETA: Maybe that's one reason for this phenomenon: people trying to sound smart instead of trying to be smart.
Link.
Given the positive reactions, I think the professor seeded them with a positive impression of the site's content.