The problem is, there were never millions at stake. Except apparently in Rwanda, but I'll get to that later.
To me the problems clearly outweigh the benefits, and not just on a theoretical level, but on a practical one. Eg. Saddam was a typical dictatorial leader. His primary occupation was staying in power. To this end he favored his Sunni muslims and oppressed the Shia and the Kurds. Several thousand people died during his rule because of the way he handled this. I'm reffering to his oppresion of the Shia and Kurds, in retaliation for their uprisings. Uprisings, I might add encouraged by the US. The wars he involved Iraq in are another matter, because they have complex backgrounds.
Through oppression he held the volatile nature of Iraq in check. He was good at it, because he knew the people he was ruling, and was pretty much a product of that part of the world. If he wasn't capable he wouldn't have ruled Iraq for more than two decades.
Then he was removed.
Whatever numbers you favor, the civillian casualties that were the result of the chaos that followed the invasion make Saddam's crimes pale in comparison.
My basic logic is this. If I, as a mere student of politics could forsee that once Saddam was gone all hell was going to break loose, its idiotic not to assume that top people in the Pentagon didn't know it as well. They knew it, yet they decided to go through with it. That would mean they simply didn't care, because if they did the most logical course of action would have been to let Saddam fall on his own. Saddam's fall was a matter of time, and it might have been the opportunity for a peaceful change of regime.
The image the media wants you to believe prior to an intervention is that you're preventing another holocaust. Thus, anything you do can't be as bad as what's already happening. This had no grounding in facts, anywhere in the world except Rwanda. Rwanda is the only proven modern genocide, where in the space of 3 months about a million people were killed. Rwanda aside, the interventions in the Balkans, i Iraq etc did nothing but add more fuel to the fire, and made the final solution much more distant.