Niall Ferguson in Newsweek notes that since America was founded through a revolution we tend to root for revolutions elsewhere. That's not a good idea because so few of them come out the way we expect. In particular, the more violence is needed to challenge the existing political order the more likely the replacement will be a man of violence, such as Stalin and Mao. So we must be careful in what we do. First, support democratic movements while the tyrant is still in power, so there isn't a vacuum when he goes. This is what we did in Eastern Europe before the Soviet Union fell. Second, exploit divisions within fundamentalist movements.
Ferguson's article is followed by one written by Peter Beinart, who offers another way of looking at the mistakes Bush II made. Back in 2002 he saw that we faced great military and ideological power. If he didn't act first the balance would tip in our enemies' favor.
That was the same argument used back in the 1950s for attacking the Soviet Union. Thankfully, Truman and his successors didn't listen, we had a fairly stable cold war (with, alas, lots of proxy battles), and the USSR eventually fell apart. An economically vibrant democracy faced an economically destitute tyranny and could afford to wait. We should have done the same in the Middle East.