Simple solution... set up a key bind (I use CTRL-ALT-Right Arrow) to skip the current song. If someone requests something inappropriate, you can just skip it quickly without interrupting your gameplay. If the idiot wants to waste all their points on stuff that isn't gonna get played, let them.
Solution 2, let your viewers police it. Remind them that 5 votes will skip a song and costs no points. Additionally, if you have it configured a single user can veto a song by spending points. This method is actually particularly effective since it allows your viewers to decide what they don't want to hear. After all, we're here to entertain them, not the other way around.