Usually this kind of sudden 180 degree political shift is associated with personal issues. Like, Peggy Noonan getting her feelings hurt by the Bush administration, David Brock having his beliefs changed by his gay lifestyle, etc.
Johnson likely had some kind of personal issue with someone.
I've been using LGF since about 9-11, and I don't see any shift at all. Just the topic emphasis on the blog. Charles doesn't play along: he is who he is. Politically I gather that he identifies himself in classic terms- Liberal, in the sense that Hayek or Madison would use. I can dig that. Since 9-11 the Community is expanding, people are doing different things, working on their own projects. It is still a reasonably free country and as far as I'm concerned people can say what they will, I don't expect to agree with them all, all of the time. Politically I consider Johnson a friend. Besides, I like his taste in music.