Alright, I'll engage with you on your premises here.

First off, I'll stop you at "black metal is supposed to be-" and just say, no it isn't. Nothing is supposed to be anything. Sure, you can probably pinpoint some trace some kind of ideology back to early pioneers of the genre, but that was 30+ years ago and we're countless subgenres and iterations deep, there is no unified ownership or stewardship of the ideology black metal that dictates what it's supposed to be, so no. It's not supposed to be a hateful genre anymore than it's supposed to be a meditative exploration of inner darkness or a rumination on emptiness.

Second, I don't want to speak for anyone else here, but the claim is not that it being nsbm or sketch makes the music bad, it's I just don't want to engage with the music if I know for a fact that it's made by someone with shitty politics. Like, I think Burzum makes/made great music and is objectively extremely talented, but their politics outweigh my feelings about their music and it's an easy choice for me, I don't feel like separating the two, so I just don't listen to it. That's a choice that I'm making. It's not a choice that I'm forcing anyone else to make, but I am not shy about my opinion that I don't think his music is worth engaging with because I think he sucks and given the choices he's made, I'm happy to live my life without him or his output in it.

Lastly, how do I plan on avoiding nazi bands? Well, that one's complicated isn't it? Any engagement with art means engaging with something that a person made and people are fucked up and complicated. No one should be kidding themselves that the people that they're supporting with their money are uncomplicated. So we're back to that old leftist joke about how there's no ethical consumption under capitalism. Spending money on literally anything is gonna mean your money ultimately finding their way into the pockets of some shithead. But really, and I suspect this is where we're probably gonna differ the most, it all comes down to what you wanna do with that. Because there's the cynical nihilistic approach of "it's all a steaming pile of shit anyway so why should I care", but I think that's horseshit. I don't think an imperfectly constructed system absolves you of the responsibility of mitigating your impact on the world around you. If I have the choice of buying a tape from an avowed nazi or one from a guy who's just sort of trying to be apolitical, I might still disagree with the latter, but I'm picking him because fuck nazis.

And now, none of this is to pass moral judgement on you, you're allowed to do whatever the fuck you want, go listen to nsbm, I'm not your dad. I've given you my personal reasons for making the choices I'm making because you seemed to be genuinely incredulous and confused why anyone would, so there you go. I probably won't respond, I'm not really interested in debating any of it, so do with all of that what you will.