And... here we jump off into the deep end of the pool. Iraq was stable under Hussein. He was predictable, in full control of the country, the military and the population. That he did so through brutal means does not change that by all definitions of the word stable, Iraq was a stable country. Now, it is anything but. It could be taken over by Shia or Shiite hardliners, become a vassal state of Iran, taken over by Al Qaeda affiliates, fracture along tribal lines (or at least even more so than it is now), collapse into total chaos, or even possibly stabilize and become something like Libya, Egypt or Jordan.
At best, Iraq is a massive geo-political problem that will fester for at least a generation. At worst, it will be a base for suicidal foes of the US.
Iran pre-1979 was stable under the Shah, who was supported by the USA. He was predictable, in full control of the country, the military, and the population. That he did so through brutal means does not change that by all definitions of the word stable, Iran was a stable country (right up to the point that it wasn't). Now, it is anything but. It was taken over by Shia extremists and has become a base for suicidal foes (and supporting puppet actors aimed at other targets doing the same in Hamas and others) of the USA that has festered for more than a generation.
I see based on your logic, the USA supporting the Shah of Iran militarily to keep him from being deposed would have been a good idea, n'est pas? I have worked with many Iranians who escaped from Iran post-1979 who would agree with you. Not that I do, though I think the USA probably would have been better off contributing to further destabilization during the recent uprisings rather than giving moral support to their current leadership.