Was Hair Metal more a fashion statement or a genre of music? I think the line is a bit blurry.
Bit of both kinda.
The underground metal scene of the time hated
it. You can find a lot of interesting stories about stuff like that.
I think there was a fair bit of talking about beating up hair metal guys in the thrash metal part of the "metal evolution" documentary series. As far as I know there was a similiar thing going on about 10 years before that in England between punk and heavy metal fans, many metal musicians despised punk and the whole punk culture. Naturally punk and hair metal were hated for very different reasons.
Lots of songs about it too, and it wasn't just limited to angry thrash bands singing about "killing posers" and whatnot. Fates Warning - Valley of the Dolls
is pretty critical of the whole hair metal thing for example, and there's Manowar's popularizing of phrases like "Leave the Hall!" (well that came a bit later but still). Basically they all thought the whole hair metal thing was too flamboyant, too poppy, too watered down, too "fake", etc.
The punk/metal rivalry died down a lot when Motorhead hit the scene and kinda bridged the gap. Punk and Metal have flirted a LOT over the years, it's the whole reason we have the various extreme metal and punk genres now.