There is a review of Slayer's new album in the New York times. It's a good review, and it says something about metal that I have been trying to convince people of for a long time - that metal bands, in all of their violent lyrics, are just singing (screaming, growling) about things that "respectable" people in suits ACTUALLY DO. That is the big difference. The soccer mom can look at a Lamb of God video and be disgusted, but it is the people in suits who are actually doing the things the band is singing about. However, since these brutal things are done by wealthy people in suits, it does not draw the same disgusted response. Metal is an art form that puts all of humanities worst traits on display in a manner that does not ameliorate anything, even if it means venturing into hyperbole. Like the review says, some take comfort in pessimism.
Another point I always try to make is that metal bands, for some reason, have this aura of conservatism even though in all of my time listening to metal I cannot name one conservative metal band. I remember a review of an Opeth (female led, extremely anti-war band) album in the metro which said "in this usually conservative genre, Opeth is anti war," which is not accurate. Metal bands are overwhelmingly left wing. Master of Puppets, considered by many to be the best metal album of all time, is entirely an anti-war album (as is "Justice for All," Metallica's next CD). Lamb of God's last album was also entirely anti-war, and even features a voice over of a marine describing some of things done in Iraq. These are some lyrics:
"Bombs to set the people free, blood to feed the dollar tree,
Flags for coffins on the screen, oil for the machine.
Army of liberation, gunpoint indoctrination,
The fires of sedation,
Fulfill the prophecy.
Now you've got something to die for,
Send the children to the fire, sons and daughters stack the pyre,
Stoke the flame of the empire, live to lie another day,
Face of hypocrisy, raping democracy,
Apocalyptic, we count the days."
Metal was made and flourished in the Reagan years, and some even attribute the rise of conservatism in America with the rise of metal. To this day, Gwar brings the "Reaganator" robot out on stage, which it slays in effigy (as well as George Bush, and at the concert I saw - Pope Ratzinger).
These bands are not trying to save the world, like any other art form, they are merely portraying something.