I think Napoleon did something worse. Regardless of your hyperbole, the invasion of Iraq failed to produce a viable state. That was probably predictable but at the time, but nonetheless Saddam had to go.
more detestable, diabolical than Nazi Germany
No, ISIS is just more adept at total war than the Nazis were. The Nazis didn't rape (many) Frenchwomen or cut lots of throats, but they didn't have to since the French surrendered. Total war is the only answer to ISIS since those are their rules. Annihilating them means lots of civilian casualties so it won't happen until we actually get dragged into WWIII.
“Annihilating them means lots of civilian casualties so it won’t happen until we actually get dragged into WWIII.”
And that will take the same pussyfooting around until it is understood that massive civilian casualties are what is necessary to end WWIII, just as in WWII.