Should we deny certain past

When we were talking about the rape of Nanking, I was surprised on how the Jap killed the citizen of Nanking, they took it like a game which is not right. Now Should we deny this history.... No, you can't deny a history, its already written, I wish I could back and prevent the dog from biting, but I can't, can i deny it no because the scar is write on me. Just like Jap hold that scar of what happen in Nanking. Should we teach to the kids, yes but in a college course, just because of the horrible thing that happen that day.