Tak at the Old Revolution mentions a reason why Americans should also be upset by the frequent visits by Japan’s politicians to the Yasukuni shrine.:

14 class A war criminals, including Hideki Tojo, the generalissimo of Japan’s military who was sentenced to death by the Tokyo War Crime Tribunal (note: did not die in battle). He, for example, approved the infamous 731 Unit, which conducted experiments on humans to develop germ and chemical weaponry and in the process murdered at least 3,000 Chinese, Koreans, and Allied POWs. He also ordered the attack on Pearl Harbor (which means he’s not only Hitler but also Osama, to stretch the historical parallel way too thin). (emphasis added)