Sadly, my Google-fu is failing me. I believe it was a This American Life episode which looked into partisan politics, and how the majority tries to stomp all over the minority at all times. When the tables are turned, the exact same thing happens again. It's always happened, and the politicians know it. They treat the minority opposition terribly, knowing full well that they may be on the on the receiving end of such treatment in only a few years. It's simply seen as the way things are done.