The article makes a very strenuous effort to make a point about something something racism in rock that sounds a bit boring and trite to my ears. After all, Bon Scott said it best years ago: In the beginning Back in nineteen fifty five Man didn't know 'bout a rock 'n' roll show And all that jive The white man had the schmaltz The black man had the blues No one knew what they was gonna do But Tchaikovsky had the news…
If you look at something like black metal and it's sub-genres, a lot of the culture and imagery revolves around satanism and European paganism; which is popular with a certain segment of European people but would hold little to no interest to those of an Afro or Caribbean heritage. Especially since so many black people have quite strong Religious beliefs. (Less so these days possibly, but many still pay lip service at the very least.)
If you then look at the 80's hair metal and glam metal genres with the emphasis on long hair and make up and an image of sexual ambiguity. I think we can all agree that there (sadly) exists a big homophobia problem amongst many black communities; which means that the aforementioned sexual ambiguity would be very off-putting to them.
Those are obviously extreme examples, but I think I've maybe made my point.
I'm probably talking out of my ass, but those are my thoughts for what it's worth.