I don't know if Japanese people in Japan are so much in denial about it, but rather keep in mind, for a long time the massacre in Nanking was not taught in Japanese history books, from what I have heard.
Japan has some horrible history in its past, but every culture has examples of a horrible past. People like to make convenient comparisons, and it seems to be human nature to omit or try to lessen the horrific acts of their own ancestors. We can say the Japanese made the Nazis look tame; I doubt anyone would say that if they were one of the Jews in the Nazi camps themselves. Horrific acts of torture and murder are a part of America's past. One example: the whites who killed native Americans, killed native women and cut off their breasts to make pouches. Anyone can say this doesn't compare to the Japanese, but torture, murder, degredation and human monsters know NO national or racial bounds. If you were one of those women, or that were your mother/wife/daughter/sister, how would you have felt about it?
As an American of Japanese descent (3rd generation, grandfather arrived Stateside in 1890s) I have been blamed for Pearl Harbor ad nauseum. There are still a lot of people today who blame all persons who are Japanese for the war, even if they were not born then, or not even born in Japan! I will NOT excuse what the Japanese *Imperial Army* did during the rape of Nanking and the war!! But to blame the Japanese people in general now for what happened 60 to 70 years ago, is pretty sad. They need to be educated about it, just as we all should be educated about our pasts, both the good and the bad.