Merzbow does not need to be justified, the guy is more metal than anyone.
I saw him play St Vitus in Brooklyn a couple years ago, fucking phenomenal gig: a prog metal hellride, a fucking journey into the beyond, far beyond any metal band's imagination or ability, harnessing noise and transporting you somewhere awesome and scary. One of my all-time top gigs: how often does a gig actually take you somewhere else? Move you? Like not just your body, but your actual imagination, making a memorable dent on your mind? Hardly ever. Merzbow is what more metal should be about. But nah, then it'd actually be scary and mean something.
Merzbow is a visionary: laughing at him in an "all things HEAVY" thread is straight-up ignorance by kids who don't know what they're talking about.