Also, if you haven't, it may be worth reading Dave's commencement address from 2005.
While the subject is religion, there is a heavy political undertone, specifically the following quote:
"I sorda consider myself in a way a non-believer. Certainly I don’t believe that I’m quite convinced in the same God that 'Shrub' does, up there in the White House. I can’t imagine a sort of Santa Claus kind of God in his long robe-y pajamas sitting there watching us, making sure everything is happy and hunky and occasionally choosing sides like he’s watching a football game, and scream 'kickass.'"
In this case, the "shrub" would have been George W Bush, who's religious beliefs were often thwarted in with his political beliefs.
In my opinion Dave's agnosticism is a partial cause of his anti-establishment sentiments, due to the fact that for most of US history, the 2 have been intertwined.
Here is the link to the full address:
http://www.haverford.edu/publicrelat.../dmatthews.htm