Yes anything can be justified in a seemingly reasonable way, a-ny-thing.
As for your second point I fail to see how targetting the Pentagon (or supposedly the White House/Senate) counts as a civilian target. The truth is there were probably much more reasonable and quieter ways to end the conflict between us and the Japanese, but we wanted to show off the new bomb we created.
However if you want civilian targets perhaps we should look at Andrew Jackson who slaughtered most of Americas living Native American population, or the blind eye we turned from 1910-1950 to the culture of lynching, even allowing the KKK to run the sheriffs offices in most states (northern and southern). And those were in our own country.