I assume you mean these events were wrongly justified by people at the time. They can't be justified by any sane morality. You can't murder an entire race of people. You can't murder one person.
I don't see how times would have changed since then. Murder is still legal and recommended in most of its forms. Genocide is still democratically supported national policy for the world's leading nations. The only case in which you can't murder is if you're not empowered enough...
Investigation of war "crimes" is a meaningless concept when (not if) only the losers are investigated. The winner of a war is automatically guilty of murder, there's simply no way around it (unless you fight wars the James Kirk way, by setting your phaser on stun). You seem to feel that necessity doesn't make murder more acceptable - so necessity can't be used as an argument in renaming murder into "military heroism", either.
Timo Saloniemi