I don't think it's just a japanese visual music thing. It's a very japanese thing overall. I don't know if it has anything to do with the second world war, but us Germans were allied with the Japanese... it was like us with the Italians against the whole world (Axis of Evil, anyone?)
After America opened Japan quite cruelly after WW2, dooming their traditions as pervert (geishas etc.) and forcing the American lifestyle upon them, I think that the Japanese still have a more positive image of the Nazis than any other country in the world.
On the other hand, Japan was always pretty fond of the old German ways of living: order, discipline and accuracy. They actually lived for the same ideals and still do. AND Heath stated that he has a friend and Germany and would love to come here again soon (so I guess he's pretty fond of this country)
If you look at the whole anime/manga AND music scene, the Nazi uniform appears again and again. Yeah, it is by now a part of the goth-style, but many manga are actually Nazi themed (which usually resembles a very strict military regime of awfully goodlooking guys who use the lower ranked ss soldiers as sex-slaves... )
I think if this style actually has a message, I guess it's a more historical thing (since they have more positive connection to Nazi-Germany than any of the Allied countries) than something about political orientation.
I don't think anyone in Japan wearing those is fascist :lol: I guess basically they just think it's damn cool and stylish for guys to wear it.
conclusion: I as German myself, who is not fond of the Nazis or any of that (especially not was going on at the moment) think that Japanese using the Nazi uniforms is something completely different. It's basically used to look good on guys (and sadly it does)