It's a pretty sane opinion to hold: basically, it boils down to "in war times, value(civilian) == value(soldier)". But I wouldn't call it "unassailable", and I'm sure many will disagree with it.
You could basically factor out all the soldiers on both sides, and the total casualty count (just civilians) would have been higher.
That's the argument, anyway. I am not any sort of military expert, so I leave you to make your own judgement. But it isn't like they had the equivalent of twitter @dronestream highlighting civilian casualties back then.
In the non-nuclear regular-old B-52 firebombing of Tokyo, hundreds of thousands of civilians died, and the entire sprawling city was quite literally burned to the ground.
https://www.google.co.jp/search?q=firebombing+of+tokyo&clien...
Those pictures don't look like reduced civilian casualties to me.
Was there any military value in bombing Tokyo, or were the civilian casualties the primary object?
The perennial "Bash the US for dropping the atomic bombs" really just needs to stop. You're judging actions that happened 70 years ago by your standards you hold today. The question you need to be concerned over is, "What would we do in this day and age faced with a similar situation?"
All that said, I'm not judging any actions, I'm not sure where you got that from. The GP said that the remarks made by the pilot were "unassailable". I just pointed out that that's nonsense because while it's a sane argument, there's also a sane argument against it. It's been many years and there's been no US bashing in this thread up until now, but absolute statements on the morality of what happened, in either direction, just don't seem to make sense anymore.
Plenty of people in the day opposed it as well. Here are quotes from Dwight Eisenhower, Admiral William D. Leahy (Chief of Staff to Presidents Franklin Roosevelt and Harry Truman), Herbert Hoover, General Douglas MacArthur, etc: http://www.doug-long.com/quotes.htm