Nothing justifies massacre -- except if you can claim that you can make a quick one right now, compared to an 'inevitable' long one, and that trade-off is worth it. (Back to square one)
You say 'all of it is wrong - ALL of it'. It implies it's equally wrong. But then, conveniently, the Japanese attacked first. So defending is kinda right, but of course it's just as wrong as mass murder of civilian populations. So it's kind of like a wrong but right necessary evil.
I think we agree, I'm just saying this because I hear way too much about 'right' and 'wrong' with armed conflict. It's all wrong -ALL of it.