Certain subcultures have a very dark nature indeed - the story of the band Mayhem is one of a submergence into insanity, depression, and suicide - these were disturbed young men and some of their fans celebrate it. This isn't healthy, but sometimes lunatics are just lunatics. It happens.
Over-analysis destroys this, as it does most art. Sometimes it isn't altogether bad to scream defiance at the universe. Sometimes the universe screams back.
Speaking of Slayer.
Slayer and Katrina & The Waves - “Chemical Warfare (Don’t It Feel Good?)”
https://www.youtube.com/watch?v=7MrMfoHejiw