This isn't about a philosophical debate where everyone can sit down and talk about what's right and what's not. It was a war, plain and simple. You end up making decisions that you'll have to live with later.
What would the costs have been if the war had dragged on for another six months? A year? Two?
If, rather than dropping atomic bombs, the Allies had formed an impenetrable blockade around Japan instead, everyone would be talking about what a shitty, reprehensible idea that was because millions of Japanese starved to death.
