People who know a lot about the exact appearance of Nazi uniforms are sorta showing their whole ass, imho.
Mike Godwin, https://twitter.com/sfmnemonic/status/896884949634232320
That is obviously a much larger set of people than closet Nazi admirers, even in the U.S.
And the previous poster might be an European from a country once occupied by Nazis, or even Germany, where such knowledge is part of the historic memory.
Most Czechs with at least elementary history knowledge could distinguish Nazi helmets from other ones at first sight; the Stahlhelm is a very distinct design and it is part of a very dark memory for us. It had some innocent uses too (Austrian firefighters or Chilean cavalry, IIRC), but it is tainted here forever.