I think it has very little to do with maturity level, that's just absurd! If anything, all this dubstep crap will be gone when people "grow up" and get out of the clubbing every night state of mentality.
There is so much more to this kind of music than just anger...
It's not really about "maturity", it's more about people listening to it when they are in their 14s-20s because of some reason unbeknown to me. Practically everyone I met back when I had said age, and practically everyone I know in here that has said age listens (or listened) to it.
And yes, there's much more than just anger, which I never even mentioned.
I don't just listen to metal...some of my other favorites genres include industrial, IDM, drone, shoegaze, post-rock, dream pop, krautrock, ambient, crust, post-punk, avant-garde jazz, minimal techno, east coast hip-hop, etc. I'm pretty much open to anything. Metal is just one of my favorite styles to listen to, and it's not because I use it as a vessel to "vent my anger"; rather, I enjoy the sound.
I know you do and that you are open to almost everything, can't you just tell I'm fucking with you? lol
And again, I don't think anger has anything to do with people liking the genre.