What drove America to commit this atrocity was trying to one up Stalin. The Russians defeated the Germans and they were coming for the Japanese next. America couldn’t have Russia win the war on two fronts, it would give the commies too much moral authority, so they used the atom bomb to show the soviets their military capabilities whilst bringing the war to a close on Americas terms.
We can mourn the loss of Japanese civilians who were immolated to further American interests in their fight against communism, and we can also mourn the victims of imperial Japans cruelty and greed in China and elsewhere. It is understandable for the victims of Imperial Japans atrocities to wish vengeance on the Japanese but the people who died were (mainly) japan’s proletariat who shared more in common with the Chinese proletariat than they did with their imperial ruling class - I.e. maybe not the right people to seek vengeance against.