I believe that is is proper to feel grief over the Japanese civilians who died. I do believe the bombing was proper and ended the war poste haste. I have never regreted the event. I do regreat that the ravages of war are sometimes necessary.
Taking it to the enemy with full force is the best way to end hostilities quickly.
Hiroshima and Nagasaki saved American lives. If those events only saved only one U.S. life, the life of a citizen or a military member of the nation that was attacked in the first place, it was worth it.
Our citizens, our military members are not expendable. If someone attacks us, we're going to put them down.
Remember that folks who think the U.S. is a pushover.