Gah, this thread is now also getting lost in generic WWII history... it is really not relevant to get into the political reasons behind the start of the Pacific Theatre of WWII! Not to mention that you spectacularly misread what Omega meant, Winddancer.
"I am become death, the destroyer of worlds," said Oppenheimer with all due gloom when the project was done. Nearly all of them were uneasy about what they were working on. But to blame the scientists is unfair for several reasons:
1. They were making a big bomb. Any weapon is unpleasant in origin but it was a war! People were making weapons all over the darn place. They were just making a bigger one. Remembering that they had no idea about the radioactive fall out, they just throught they were making the largest yield bomb yet seen. If you are going to pillory them for that, would you also pillory the scientists that developed the incendiary mechanisms used on Germany, which killed FAR more people and were at least as horrible as the atomic weapons used on Japan? Like I say, it was a war, and it sadly becomes the purpose- even duty- of scientists serving their country in war to create better ways to kill people, as that is what war is all about. Yes, wouldn't it have been nice if we hadn't had to have had that war... but we did, so there you go. You cannot limit that war with rules once it starts. Scientists design weapons, engineers build them, soliders use them. It is unfair to hold them accountable for doing their duty by arms. So there is no question of their motivations- developing a new weapon in defence of the free world. If it not right to hold them more accountable for developing a bomb for that use than it is to hold people accountable for using tanks, guns and knives.
So as I say. Big bomb. What reason would they have had to say "actually, I am not going to make this...". The logical extent of that argument is to say that no-one should have designed any weapons for the US ever. In which case, they would have lost.
2. At the point the project was commenced, it looked rather essential- Germany was working on the same project. In short, the bomb was going to be discovered sooner or later. Frankly, better by the US than by many of the unpleasant forces in the world that may otherwise have gotten it. As it turned out, Germany lost out by conventional means first, but the risk assessment from Germany was fair.
3. They did not know the implications of what would result from nuclear weaponry. I am sure if they had seen the Cold War coming they would have hesitated.
But as I say, ALL they were doing was making a big bomb in order to aid their country, which was hardly ascribable as an evil act in the middle of a global war for survival. Wars need weapons. People who fell behind in the tech race would lose. The scientists provided and did their duty as much as any soldier did.
No, we cannot blame scientists for developing the bomb- they were people simply responding to the needs of the time. The moral debate, surely, has to be about the decision to use it. That is the only interesting part. That is where thje controlled part of it was. The bomb was going to be designed, and built, and would be dropped by airmen oif so ordered. But did that order have to be given? Once the bomb was there, can any justification be made for its use if it was not necessary? And was it necessary? These are the two relevant questions.
And as I say, the answer to the second is that we will never know.