Black metal clearly harbors the most pretentious musicians/fans and I say this as a black metal fan
If you may as in music as a whole, I would argue you this to the death but this would take me more to the post-mysterious guy hardcore world than metal itself. Though, I see how in metal black metal could be seen as pretentious by you though I don't agree really...
Honestly, I have met very few "pretentious" black metal musicians/fans in my life and I feel like I've met a good amount of people associated with the genre on both ends of the stick. Again, metal to me strokes a certain fantastical/escapist mentality more than any other form of music. I believe it encourages a certain camaraderie unlike any other forms of music, though there is a undeniable analogous relationship in the noise/industrial underground but even that is a little bit more "legit" in it's topical matter for a number of reasons I can explain elsewhere. A lot of the rhetoric about misanthropy, mysticism, satanism, snow, winter, beautiful wolves running through the rain, isolationism is nothing more than a stylization built around a long running tradition. I also think people forget how successful metal music truly is....it is pretty astonishing. For all the nihilistic and anti-human rhetoric, there are a lot of underground people living pretty well off their bands, labels, metal-themed pubs and breweries, and whatever else. Metal fans spend money like its no one's business. To me, most people want to talk about black metal in a way that isn't really pretentious so much as it is studied and almost dialectical because that in and of itself is fun.
However I don't want that to dismiss it what makes the fantastical element important - it simply stimulates the minds. It creates a musical and cultural vocabulary that is very creative and otherworldly. Furthermore, I truly think it does allow people to think intellectually about things in a way that is really rewarding. I mean, its both fun to think about a bunch of wolf-dogs running around the snow and licking each other (I love wolves) but on the other hand, what does that imagery mean? It's important, you know?
HOWEVER PART. 2 - We all know Blasphemy is the real deal, if you know about the Ross Bay Cult. They aren't nice guys. A lot of trad. black/war metal - not really speaking about the Norway scene but I guess I am kind of - and what comes out of the original bands has something to do with a real deal toughness and brutality that I've seen extended to some gritty parts of real life. Dudes and ladies that thrive off being outlaws and listening to
Fallen Angel of Doom and dusting off a line of blow before knocking some fuckers out in some dive-bar. But that's another story.
Maybe that's kind of worthless input though....I don't know....