Killing Jews was done on a regular basis in Europe and seems almost something like a ritual. In my darkest moods I think that Hitler did what Europe wanted to do. Anyway the leaders knew about the slaughter of the Jews and could have at least hampered it. They chose to ignore. In that respect there seems to be a similarity with the Pacific War: the higher echelons in Tokyo knew what was happening in China and other parts of the world where the armed forces went berserk. Powerless to stop it they chose to ignore it. Also some degree of disinterest surely must have played a part.
Many people were at that time attracted to the nazi ideology and indeed many helped to round up and transport the Jews to the death camps. Although they might not have known the extent and length the nazi's were capable of going.
Though it must be said that the Danes were the exception. It is possible that some Danes joined the SS, but when the occupying Germans decreed that the Jews were to wear the yellow star the Danish king put one on his breast saying that if his subjects have to wear a yellow star he will do that also. And many Danes followed his example. So hardly any Jew was taken from Denmark.
I think the main reason the former colonial powers are focusing on Japan's war past is because they felt thoroughly humiliated by a people they considered inferior. Especially in a time when the white man thought he had the god given right to rule over the non-white people, the shock must have been great. Listening to the camp stories the most hated thing was not being beaten or hungry, but the obligatory bows to the Japanese officers or in the direction of Japan. On a site dedicated to the Tjideng camp (unfortunately I am not allowed post a url, but just google tjideng and look up the site: members.iinet.net.au/~vanderkp/tjideng.html) the first picture is that of European women bowing. You would expect pictures of mistreated women, emaciated perhaps, but no, just a row of well fed European women in a row bowing. It was presented as something horrible. If you understand that then you will understand where the hatred comes from