You don't understand. The current school of thought is that had Saddam been left in power, and then his sons, there would never have been WMD developed, since we can't PROVE he would have developed and/or deployed WMD, despite his monomaniacal pursuit of such weapons in the face of world opposition for decades.

There would have been no more murders of his own people, since we can't PROVE he would have killed hundreds of thousands more people, despite doing exactly that in the past, killing almost a million of his own people over past decades.

You can't match the thousands of unfortunate deaths from combat with the hundreds of thousands of theoretical lives that would have been saved, since the latter are only theoretical, and past behavior is not absolute (the favorite word seems to be "empirical") proof of future behavior.

In fact, there is absolutely no proof whatsoever that had we not invaded Iraq, that Saddam would not have converted to Bhuddism, opened his nation up to democratic rule, and taken up knitting.

That's LOGIC, see?