Not only Hiroshima and Nagasaki but also killing defenceless civilians in the Vietnam War? If just because it "shortened the war" It just doesn't add up or, do I miss some points? Please enlighten me.
There's always more that can be said, but you might like this older thread from /u/Restricteddata;
Seeing as this thread got pretty popular, you might also enjoy these other answers by the same author.
Was the US ever tried for dropping the Atomic Bomb on Nagasaki and Hiroshima?