I’m sure there is a way for the song’s owners to remove themselves from the license agreement, but as I said, if they are making a public stink, that should be reason enough for the campaign to stop using the song.
A guy like Rush Limbaugh can keep using a liberal group’s song for decades just by paying the license fee and not worrying about the owner’s griping (as he has,) but in a campaign you have to think about “winning the battle but losing the war,” and it just isn’t worth it.