Jesus himself was criticized for associating with sinners, to which he replied that he came not to call the righteous, but sinners.
While I despise most of the things that Obama stands for, this is a wonderful opportunity for an evangelical Christian to share his faith. As Jesus also said, You are the light of the world and to let your light shine before men.
or will it be a PC de facto blessing of the incoming administration?
If it's the former, you have a point - he should do it.
If it's the latter, it "constitutes material cooperation with intrinsic evil".