You must be joking, just look at the world you live in, no one cares about what had happened in the history, that's why it keeps repeating itself. By reestablishing civilization I suppose you meant reinventing drugs, weapons, prostitution and so on. They've clearly spent some time reflecting upon history. I think everyone is equally vulnerable and won't show much of a resistance if you go and shoot them in the face. That isn't really a valid excuse. In my opinion, the life of an adult is more valuable than the life of a child. Both for the adult and for the society they live in. A child can be replaced much more easily.