Two words actually, The effect reffered to in this clip between Susan Glasser and Steven Colbert:

This is known as the “Lucifer Effect” as explored in The Lucifer Effect: Understanding How Good People Turn Evil (Random House, 2007). By Phillip Zombardo. This book is a well researched piece of social science which extended to the edge and some people believe beyond the edge, of ethical human psychological experimentation. While there are some surprising cases of group dynamics, Zombardo does also note that these studies are only valid for the groups found in college and university settings, which is not a reflection of the general population or human nature. Though if your government seems like it is run by high school students and all the petty social dynamics that entails, these insights might serve as vindication.