That's a deliberate, straight-out repudiation of God. The notion that good ends justify evil means is a moral theory condemned ever since St. Paul wrote Romans 3:7-8:
"But if through my falsehood God's truthfulness abounds to his glory, why am I still being condemned as a sinner? And why not do evil that good may come?—as some people slanderously charge us with saying. Their condemnation is just."
Some people say it depends on whether they thought the Japanese were on the verge of surrendering before August 6, 1945 --- or not. I would not be the one to make the call on that, because I haven't got the military experience and expertise.
But some people DO have that kind of expertise. Historians record that most of America's WWII military leadership thought Japan was already n the verge of collapse before the atom bombs were used:
http://www.freerepublic.com/focus/f-news/3321050/posts
"Six of the seven five-star generals and admirals of that time believed that there was no reason to use them, that the Japanese were already defeated, knew it, and were likely to surrender before any American invasion could be launched. Several, like Admiral William Leahy and General Dwight Eisenhower, also had moral objections to the weapon. Leahy considered the atomic bombing of Japan “barbarous” and a violation of 'every Christian ethic I have ever heard of and all of the known laws of war.'"
I don't think these American military leaders were pinkos, pacifists or fools.
But the real problem isn't not that the Hiroshima/Nagasaki bombings were strategically unnecessary. The real problem is that, in terms of an ethic of killing, there is a difference between targeting soldiers/combatants/military assets, and civilians/noncombatants/civilian values.
Most people in the world today at least profess to recognize this distinction (except for ISIS and their ilk).
It's hard to put it any clearer than this:
"Any act of war aimed indiscriminately at the destruction of entire cities of extensive areas along with their population is a crime against God and humankind itself. It merits unequivocal and unhesitating condemnation." (Gaudium et Spes, para. 80, 1962)
Utterly crushing the Japanese military/political machine would have been justice. Incinerating civilians with a deliberately indiscriminate weapon of mass destruction, was murder. That should be clear when you consider that General Douglas MacArthur and his staff wrongly succeeded in exonerating Emperor Hirohito and all members of the imperial family from criminal prosecutions.
Thus in the end, 250,000 civilians were killed, and the Emperor Hirohito was not.
Please compare and contrast the atomic bombing of two cities, and the incendiary bombing of over two dozen cities. Do you see any moral distinction between, let us say, the atomic bombing of Hiroshima and the incendiary bombing of Tokyo?
...”The notion that good ends justify evil means is a moral theory condemned”...
Ummm...
God command the extermination/genocide of the Canaanites, women and children included...... God did not order the extermination of these people to be cruel, but rather to prevent even greater evil from occurring in the future.
In 1 Samuel 15:2-3, God commanded Saul and the Israelites,.....
“This is what the LORD Almighty says:..... ‘I will punish the Amalekites for what they did to Israel when they waylaid them as they came up from Egypt. Now go, attack the Amalekites and totally destroy everything that belongs to them. Do not spare them; put to death men and women, children and infants, cattle and sheep, camels and donkeys.’”
God knew what the results would be if Israel did not completely eradicate the Amalekites. If Israel did not carry out God’s orders, the Amalekites would come back to “haunt” the Israelites again and again.
God ordered similar things when the Israelites were invading the promised land.... (Deuteronomy 2:34; 3:6; 20:16-18)
....to the Canaanites, God commanded,...... “However, in the cities of the nations the LORD your God is giving you as an inheritance, do not leave alive anything that breathes. Completely destroy them — the Hittites, Amorites, Canaanites, Perizzites, Hivites and Jebusites — as the LORD your God has commanded you...... Otherwise,..... they will teach you to follow all the detestable things they do in worshiping their gods, and you will sin against the LORD your God” .....(Deuteronomy 20:16-18).