I agree that it had great psychological impact, giving the Japanese military the excuse they needed to quit.
But from a moral perspective the difference seems like that between killing several people with a pistol or a grenade. Doesn’t make much difference to the victims.
True and given the fact they many died quickly during the initial blast it was more humane in some instances. (they were better off than being burned alive during the fire bombing of say Tokyo)
Of course those who died later from radiation poisoning weren't so lucky.