I thought about Joe's post: Politics Trumps Morals referenced below. For lots of folks, I think it is not so much politics that trumps morals, it is anger about politics. When you are still blind with rage over Bush v. Gore (or Clinton v. Lewinsky) you can't see your own behavior rationally enough to avoid immorality.
To test this, image some policital event which would really enrage you, then imagine your reaction. Does immorality emerge?