I'll help you better understand Japanese culture.
I am not approving of Imperial Japan's or Watanabe's actions but in the eyes of them what they where doing was not as horrible as Americans see it. What I mean is that in the Japanese culture it is seen as rude to show pain or discomfort if you are given a punishment you deserve. Especially if you are a man. You would be seen as selfish and cowardly. This is why suicide is such a big issue in Japan. They believe that if you deserve to die and don't commit suicide then you are a selfish coward. This is also why Yakuza members cut off their own fingers as form of punishments.