Lest you forget, while installing dictators and facilitating genocide is bad enough, the US also oppressed civilians during the time. Mississippi, for instance, was a police state with apartheid a good 20 years after the end of the war. Americans with Japanese heritage were forcibly removed and put in concentration camps.
Suffice to say, your moral high ground is not as clear cut to me, especially when you talk about justifying the atom bomb.
I'm not saying the US was always right - I'm saying that having the US win was a better outcome than the other alternatives. Would you agree with that?
And I'm not justifying use of the atomic bomb in every scenario, or even saying that it was the best possible outcome, but out of the options available to Truman, it appears to be the one that would have resulted in the least amount of suffering.
Suffice to say, your moral high ground is not as clear cut to me, especially when you talk about justifying the atom bomb.