This divorces it from context. There is no point showing children context-free images of atrocities except to terrify them. Even within context, it's really not the best thing to show children under a certain age. My family is Jewish and my father lived through WWII in Britain waiting to be invaded and thrown into a concentration camp, so he made sure I saw Holocaust images when I was pretty young and I can't look at images of atrocities anymore because they disturb me too much and give me vivid nightmares. I even have trouble with horror movies. I basically avoid them. That's not how you let a child know what war is or what genocide is.