Three points:
1. From link: The ORB poll estimate has come under criticism in a
peer reviewed paper entitled "Conflict Deaths in Iraq: A Methodological Critique of the ORB Survey Estimate", published in the journal
Survey Research Methods. This paper "describes in detail how the ORB poll is riddled with critical inconsistencies and methodological shortcomings", and concludes that the ORB poll is "too flawed, exaggerated and ill-founded to contribute to discussion of the human costs of the Iraq war".
2. Vast majority of civilian deaths caused by insurgents and terror groups sponsored by Iran and Russia.
3. More people were killed by Saddam and sanctions due to Saddam prior to 2003, including not one, not two but 3 gas attacks - Halabja, Anfal, Ghouta. In total Saddam was responsible for the deaths and disappearance of up to 2 million Iraqis during his rule and sanctions led to the deaths of 1.5 million more indirectly. There was no choice but to remove him, the criminality was in not doing so in 1991.