How do you know that? Have you dressed as a Nazi for a party? I haven’t. I would require a thorough investigation. I think only three types of people wear Nazi uniforms: Nazis, actors who play Nazis in movies, and World War II recreationists. Harry doesn’t strike me as the last two.
[True story: I had a friend, who was Chinese, who played a Wehrmacht officer in WWII recreation activities. He told me once a police officer pulled him over and saw the uniform.]
As I recall it was a general (costume?) party...I think his brother went as a lion.