They have no organizing principle with which to structure their own thought-life, because they don't want one. They like it when the world and their own minds are moving like a music video. It's acid without the needle.
You can see what the liberal mind thinks is really neat-o by watching West Wing. Really fast, snappy patter. Verbal cleverness. Strings of facts and figures used like Monet's paint -- to suggest a conclusion without having to clinch a long rigorous argument. Lots of violin music moments (West Wing has lots of violin music moments without the music) and free-association masquerading as thinking.
Anybody who speaks in direct declarative sentences is "dim". Anybody who talks and thinks like Robin Williams is "intelligent".