I have no pretensions of knowing the answer to the title question, but after the "Magic Negro" song scandal broke, I really started to wonder.
The only explanation (assuming we're dealing with rational self-interest, even if it's immoral) is that there's an internal struggle going on, and someone was trying to smear Chip Saltsman. Of course, you wonder what Saltsman was thinking doing something like this in the first place. Regardless of your reaction to the song parody, at the very least the guy must be a moron to be a political professional and still record (or be associated with) something like this.
The end result is that the whole Republican Party ends up looking like it's run by racist grandpas. Good going guys. That'll really help the country in the 2010 and 2012 elections.