Some acts are unjustifiable no matter how hard the perpetrators try to rationalize them. Bombing of Hiroshima and Nagasaki are undeniably among those. I firmly believe that the War Crimes Trials after World War-II should have been conducted even on some men of the Allied powers.
If it’s any consolation (although it’s not), the horrible aftereffects and the monstrous destructive power of nuclear weapons that the whole world came to realize after Hiroshima and Nagasaki might have kept a leash on the two world powers – USA and USSR – from using it during the Cold War on each other. Whatever other puny reasons the wartime experts might have had at that time for using the atomic bombs on Japan, one major fact remains to be pondered upon more deeply for the sake of our consciousness on being humans that the Japanese were used as lab rats to test the new weapons of mass destruction.