There is a lot of pent up anger and scores to be settled now that Iraqi's are free. It's not pretty, but we should not stand in the way either.
When we took over Iraq we knew there was three major groups who did not like each other - Shiites, Sunni and Kurds. Kurds were our best friends, Shiites neutral but the Sunnis were the pricks. Since the Sunnis jointed Al Qaida to kill Americans at the beginning, we should have backed the Shiites in rounding up all the Sunni Baathists and had them all tried for war crimes and shot. The Sunnis only represent 20 percent of Iraq and the Shiites 60 percent. With US backing, it would be a one way civil war, and within one year, half the Sunnis would have fled to Syria or dead. We made a mistake by ignoring the brutal wisdoms of the past and tried to do it the idealistic American way. I think President Wilson learned a bitter lesson after World War I, the US ideals are unique and the rest of the world doesn't practice it. GWB is learning that now, and future American President are not going to risk their political careers trying to reform the world again.