Suppose the US had simply offered Saddam and his government $500 million to quit (to create a democratic infrastructure before retiring into luxury). While placing a $500 million price on his head. (encouraging freelancers from around the world to take him out.)
Couldn't this have solved their problems for around a 40th of the current cost? And without either civilian or military casualties
OK, so Saddam is mad and proud. But $500 million is a lot of money. Wouldn't you be tempted? If it was cash, in your hand, and you could spend it on anything you wanted (except buying weapons, of course.).
I guess the argument against this is that it will encourage dictators. But would it really? Dictators can't do it on their own. They need a context, an infrastructure. Most of them come to power in adversity and during civil war. Buying off potential troublemakers early is maybe the cheapest way to maintain a world where such conditions don't arise to begin with.
Of course, no one likes to see evil rewarded. But there are plenty of evil bastards in capitalist democracies, running the corporate world. Arguably they do less harm there than in the strifezones where they become local warlords. Their agression is channeled into competition rather than killing.
Why don't we like to see evil rewarded? Probably because we have an instinctive urge to, as the game theorists put it, punish cheaters. But perhaps this instinct, like a sweet tooth, doesn't serve us well out of the context where it evolved. In a world of WMD, international treaties and big stakes, maybe our instincts are leading us astray.