R. Paine wrote an excellent post about the difference between disagreeing with the president on policy and trying to turn him into some kind of demon. Here's a choice paragraph:
I object when people sell that disagreement as meaning that the President is something, a sell out, corporatist, liar or pawn. Disagree with the policy, fight that policy, organize, petition, call, write, fax but leave the conjecture of what it means to history of more than twelve months.
Very well said.