Unfortunately we do not live in a world where pure points of doctrine exist. Often it is a case in war where every choice is doctrinally "evil".
The notion that there is some sort of pure doctrine that can be imposed in all cases is an interesting class room exercise, it is extremely naive in dealing with problems in the real world.
Your argument rests of false notions of moral equivalence. That some how the Japanese and the Americans were on an equal moral plain. No they were not. The Japanese were the aggressors. It is a total sophistry to assign them to the same moral plain as the victims of their aggression.
This is one of the absurdities of modern theologians. They want to argue that it was some how immoral to use the Hiroshima/Nagasaki bombs. That we could of Besieged the Japanese.
That utter nonsense. The infrastructure of the Japanese islands was breaking down. Japan could not feed it self and rely ed on food imports. Instead of killing Japanese Civilians in the tens of thousands. The Leftist Siege would of killing millions from disease, starvation and malnutrition. EVEN then there is NO indication that would of broke the Japanese will. Japanese soldiers hung on various pacific islands for decades after WW 2 ended. Even after the bombs dropped die hard militarists tried to stop the Emperor from surrendering.
Then their is the question. What response would the Japanese been to an invasion and occupation. The Left screams about the Iraqis Insurgency what do you suppose a Japanese Insurgency would of done? Also, who knows if the Japanese would of survived as a people? The Civilian and Military casualties on Siapan and Okinawa were horrific. Give the intensifying tempo of suicide attacks,the fire power brought down on the Japanese Home Island prior to and during an Invasion would of killed tens of thousands if not millions of civilians as well as military forces.
So while remaining doctrinally "pure" you would of been guilty in fact of genocide.
You speak the truth my friend and do so wisely..