Except they (the ones who did it) are already dead!
Sometimes I imagine a conversation I would have with Mohammed Atta....."How could you do this, you stupid, horrible &*$%@%? How could you spend, and end your life this way? How could this be so important to you? How could you think God -- any God, would ever support something like this?"
Some might say we reap what we sow, with Hiroshima in mind. But this is different from the traditional kind of war. I think the evil originated in the mind of one man --Atta -- and that he got funding from a variety of sources. And his great revenge was that no one could exact revenge upon him.