The influence (or overuse) of BM as a label must of course be linked to its general trendiness. Being a longtime follower of crust I thought it was quite peculiar when overtly BM influences found its way in. There have always been metal in crust of course - from Amebix-derived bands like Misery and Axegrinder and onward, and Venom or bathory has always been a huge influence on a lot of bands and people I know, but when I was a kid the connections to "black metal" as a subculture was quite difficult and best avoided out of ideological reasons. Perhaps it was different in other countries, I wouldn't know. Of course, now the mainstream assimilation of BM has washed all sense of threat and ideology away (at least in the public eye) which makes it accessible for anyone who wants it. Just like when you talk to people who believe punk was only this rock'n'roll thing which ended with the Sex Pistols, as if DIY-culture never happened. With old time legends buying in to the hype and enjoy the newfound fame (one must assume) and so the whole thing becomes justified and everyone believing that the view on black metal always was this friendly clownmusic with face paint. I do agree with the idea that you should, as an "underground" scene avoid all attempts at appropriation by "manstream channels" but I don't think it can be done completely.
Now I think this is very much part of the postideological ironical-liberal hegemony - where nothing is real, nothing is serious and everything is a product for consumption. Some people become profoundly shocked when they realise there are actual "nazis" (or people with any kind of sincere belief, left right or nada) playing music, doing art etc - since culture is perceived as the domain of liberal flimsiness and simple ironic flirtations.
