It doesn't contradict our policy, and in my opinion it's a silly position.
Do you cease watching your cable or satellite provider because some of the ads on some of the channels are political? Or listening to radio stations, or reading newspapers or news sites? Do you stop using Google or Bing search because there are political ads on the results pages?
In any event, you always have the option of changing the channel, be it here or anywhere else.
Would it be okay if Romney was the one currently buying a lot of internet ad space?