You can argue all you want. The killing of hundreds of thousands by dropping the atomic bombs saved millions of lives, mostly Japanese. By this point of the war, American soldiers had become quite efficient and calloused to killing. They would not have hesitated to kill and destroy whatever they had to to save the man next to them.
Strange that the opponents of dropping the bombs only mention the cruelty of the decision and omit the mindset of the Japanese war mongers who were prepared to allow the death of millions.