Utter nonsense. Nagasaki and Hiroshima were targeted specifically because they were heavily populated civilian areas. The whole idea was to shock the Japanese imperial command into surrendering by demonstrating the horror of the bomb. It was a cold, calculated and deliberate attack on a civilian population.

The A-bomb wasn't produced to destroy factories, and nobody in their right mind believes that was the intent at Nagasaki and Hiroshima. And even if it were, the fully predictable and inevitable collateral damage would still have made dropping the bombs morally unjustifiable by any reasonable standard, and certainly by the standard of Catholic moral teaching.

I don't judge Truman or the U.S. military. I'm sure they did what they thought was right. But what they did is still objectively horrific, and nobody who rationalizes it has any ground to stand on in criticizing the brutality of others.