Well, people will argue till the end of time about whether proportionality was judged correctly on that day. My opinion is that nobody really knew what the first bomb would do, and when it did all that and the Japs still wouldn't surrender, it was a ligitmate case of 'well, hell, if that doesn't stop then what else will but a second helping?'. It was act of desperation to get a very ugly and costly war to end. In desparate times, survival overules everything, we can agree on that.
But we are a million miles from desperation right now. This isn't The Alamo. They don't have us surrounded, and so a survival mindset that involves reverting to savagery isn't necessary IMHO. And I believe nor will it ever be with regard to this particular enemy in the future. In fact, in this war, I believe maintaining our dignity in the face of the enemy is the surest way to defeat him. To treat him as he treats us serves only to fatten his ranks.
US forces could of cut and run, back to defend our island. In fact that is probably what America would have done if we had the kind of leaders we have today.
But with the lack of political correctness (Which you promote based on your value judgments) we did the right thing.