"The use of the atomic weapon was a necessary moment in history. We have no regrets".
It was their duty, and it's silly to blame the crew.
But IMHO it could be more polite to say they are sorry. They didn't know what they carry in a bomb bay.
A "necessary moment in history" it was mostly to show USSR that "allies" have another instrument of mass-destruction against us. Atomic bombings were used as a back-up during negotiations in Potsdam.
At the same time Soviet Army crushed Japanese continental forces in Manchuria and Korea, exactly according to an agreement from Yalta conference - no later then 3 months after a Victory in Europe.
Sorry.