violated a standard that even Pol Pot and Idi Amin dared not violate.
That's... not the way too look at this.
They had other ways of killing, not that those were better. It's hard to distinguish one premeditated murder from another. The Romans cast Christians to bears, lions, and tigers; Nazi guards entertained themselves on occasion by letting underfed dogs attack helpless prisoners. The juvenile-delinquent culture of the Middle Ages burned witches and broke heretics on the wheel -- or was it the other way around?
The world did nothing to Saddam Hussein for gassing the Kurds. He might have been tried, and likely hanged, for that, but the Iraqi tribunal that convicted and sentenced him to death found him guilty of an earlier, less-well-known atrocity.