A good part of talk radio’s appeal to conservatives is the convenience of listening while working (or driving to work). Somehow, there’s a disconnect in liberal-land. Fewer of them seem to need to be able to concentrate primarily upon teh task at hand whilst lending an occasional ear to the voice in the background.
The reason liberals do not listen to talk radio or liberal TV commentators (Olberman) is because they do not want their beliefs challenged, even from those on their side.
Liberals are so stubborn in their thinking that they are disinterested in facts because those facts may conflict with their thinking. Conservatives are always looking for facts to support their thinking.