I guess the answer to the question in the OP is that the liberals are too oppressively irrational to be debated with.
Based on my observations of this thread, it might be because some of the conservative members feel outnumbered and would much rather cruise around in the waaaaaaambulance listening to the cure.
I think that it's because ustwo hasn't posted much at all since the election, and he was kind of an inspiration to many of the conservative posters.