[ZenoArrow]

Maybe someone can recommend a documentary, but I think the thing is that there's a difference between enjoying music and buying into a lifestyle. I can't say how your son sees it, but he may just like the music.

If you look back at the music you enjoyed in your youth, I'm guessing you could find some music you like made by people with a questionable moral compass. However, you don't have to think about such things with music, sometimes it's just about the way it sounds.

If you're concerned about your son, why not see if you can broaden his musical horizons outside of metal, maybe there's something you'll find that you'll both enjoy. If you'd like a starting point, perhaps your son may like some classical composers like Bela Bartok, some of his pieces are easy for metal fans to appreciate:

http://youtu.be/YOcvPaFY9UE