Having found a description of them, I would say they do not "forget" but choose not to learn.
They were not there so have nothing to "forget". I don't suppose many of these offensive but really rather childish clowns were even born before the1960s. More likely they deliberately ignore the Nazi regime's utter barbarity, but proudly support Hitler's racism including anti-Semitism, and homophobia.
My, aren't they brave! I expect they have looked at plenty of photographs of the real Nazi rallies and the like, and were impressed by the smart parade uniforms and trappings but failed to spot those 1930s men, for all their evil intent, did not hide behind face coverings.
I thought it rather ironical that this anti-freedom outfit's founder had been a Marine in the service of the nation that calls itself "The Land Of The Free" in which people like these ones have the right to proclaim their anti-freedom mantras.
