The problem with logic based on one wrong assumption (that Japan did not willingly and actively use murder, rape and, torture to subdue civilian populations) is that the internal arguments are very logical and rational. However, that does not make them correct, right or, sensical to people who have not made that one assumption. I recommend you read a little more about the war in China during WW II. I'm the last one to think that just because the majority believes one way that, it must be correct. However, in this case we are and you are wrong.
How do you know any of this? Were you there? There were beheading competitions and such but it was not systemic. Not at all. These were exceptions and performed by excited units. Can you fault an entire army on the actions of a few? Like I said, the Japanese may not have treated their own in the same manner but it's not as if death was not a part of life in Japan...