gwern might be a smart guy, but he is below average at charitably interpreting opposing arguments, at least this is my impression based on my interaction with him here and on IRC. It's not an uncommon failing, Eliezer comes across as uncharitable, as well, especially when dealing with those perceived as lower status (he was very very charitable to Karnofsky).

Of course, the impression of uncharitabilty (uncharitableness? is it even a word?) is often given off when the person is a few levels above you and goes through the most charitable interpretations of your argument in their head quickly, realizes that they are all wrong, as well, and rejects the argument without explicitly discussing why the charitable versions are no better than the uncharitable ones. I don't know how to tell the difference.