I think there are a lot of people out there that would disagree with the "last option" part of that statement - including the fair majority of the scientists actually involved in the development of the atomic bomb.

I did an extensive report on the Manhattan Project in college, and I came to an opposite conclusion. There was some apprehension, some regret, and some dissention amongst the scientists, but from my research, it looked like when the final decision was made, most of those involved realized the need for the action that was taken.