Which bit did you miss?
That's not a true point, and that's why different nations have different ideas and customs. Some are isolationist, and therefore not a member of a "world" society
In the end, the Germans were their own society and, therefore according to you, had every right to do as they please. They, the "society" decided it was OK.
Therefore the people attacking German society to force their own "right and wrong" are no different than the Crusaders or Islamic armies that conquered for the same reason