That was an act of war conducted by one sovereign nation on another,
I disagree, it was an unnecessary act in the closing moments of the war, when Japan was already finished.
To drop one bomb was very nearly justifiable, but not quite. To drop two was totally unjustified and unforgivable.
The US was achieving much the same effect with saturation bombing - it was an experiment to see the effect the bombs would have and to scare the Russians.
and the fallout was an unintended consequence.
It was well known beforehand there would be significant radiological effects and there would inevitably be severe consequences, there was no way of knowing exactly what they would be until they tried it.
Its easy to argue the whole thing was an open air experiment on civilians - men, women and children - conducted by the US Army.
The Nazi's did their studies intentionally against prisoners.
The first two nukes were intentionally dropped on many thousands of civilians. Pot-Kettle?
Its possible to argue, the Nazis subjects were lined up for a horrible death anyway, why not use their deaths for the betterment of mankind?
The US ideology was it was better for two hundred thousand Japanese civilians to die than the same number of American soldiers (when actually they probably wouldn't have).
I wouldn't support either ideology when there are better alternatives.