What I find funny is how the US is perfectly fine with bombing other people, but as soon as someone bombs (i.e. 11/9) them, it's all "this is the worst thing ever quickly we must invade various countries because terrorism".
Well, we make at least a token attempt to attack military targets. The World Trade Center was not a military target.
Anyway, as stated above, Hiroshima and Nagasaki were indeed valid military targets.
Hiroshima had a military port, was home to the headquarters of Japan's Second Army Group which was responsible for the defense of all of southern Japan, and was also home to the headquarters of at least 3 other military formations including the 59th Army, a logistics base with a large stockpile of war materiel, and an assembly area with 40,000 troops stationed in the area. It was also undamaged by air raids, because it did not contain aircraft manufacturing infrastructure that was the primary target of conventional bombing raids.
Nagasaki contained one of the largest seaports in the region, as well as Mitsubishi Shipyards, Electrical Shipyards, Arms Plant, and Steel and Arms Works, employing nearly the entire population of the city. It was a gigantic industrial target, but also difficult to locate at night with RADAR due to the surrounding geography, making it untouched by firebombing.
While I do not approve of the bombing of civilians with any weapon, conventional or otherwise, it cannot be denied that the industrial and military infrastructure in these cities were valid targets of military action. It also cannot be denied that a conventional invasion would have cost far more lives, both Japanese and American.
I say this as an American with a Japanese-American grandmother and half-Japanese mother.