> (And even if it was "that a land-based invasion of Japan would be extremely costly for both the invaders and the civilian population" still wouldn't justify nuking civilians. War crimes are not excused when they make one win more cheaply).
War crimes are not, in themselves, "programs of systematic and indiscriminate extermination" as claimed by OP, unless they are part of a wider policy. I'd argue if the US had the intention to conduct such a policy, the results would have been very different (as can be deduced by looking at successful genocides).
> Why would they want to annihilate them? They wanted to win the war.
Exactly.
> If anything of the kind was done on their own soil of course, they'll still be screaming bloody murder for all eternity (like Pearl Harbor, even though they purposefully provoked Japan for months before it acted).
I agree that Pearl Harbor needs to be seen in the wider perspective of the US-Japan relationship. And yes, most countries are a lot better at forgetting slights against them than the offenses they themselves committed (ironically enough, both protagonists of the conflict are an excellent example of this problem).
It seems to me that you are arguing that the US disregard the human cost of their foreign policy and have little regard for "collateral damage", not that they have been engaged in some bizarre extermination program of Asians, which is what OP was suggesting.