Maher is a liberal leaning comedian, yes. Dennis Miller is a newly converted conservative leaning comedian. Does it make either of their points any less valid because they are comics, or liberal, or conservative? NO, I enjoy them more, and am more driven to thought on issues by a good political comic than by the stuffed shirts like Stephanopolis or O'Reilly, who purport themselves as experts on everything from defense to foreign policy to economics to supreme court rulings.
Comics present the point in a different light and force you to examine it in a manner different than you have in the past. The stuffed shirts tell you what to think, they leave an audience no room to fill in the blanks, good comics do.
I seem to have heard of some guy called Will Rogers who was a comic yet had wry, observant witticisms. Were his points less valid because he was a comic, or a country liberal?
Hating Maher because he is a liberal is lame.