One point to consider is that at the time of the attack, Hawaii was not yet a state.

Many islands in the Pacific were occupied by European nations; the Philippines, Hawaii and several other islands were occupied by the U.S.

The Japanese bombed and invaded almost all of these islands. The target in Hawaii was the U.S. fleet. If these armaments were in, say, Hong Kong, they would have been bombed there.

There are many Japanese atrocities. And the U.S. has its Dresden and Hiroshima et al. All qualify for war crimes status.

But Pearl Harbor was a legitimate military target.