You have no grounds to stand on. No evidence to prove your case.
You do know that many of our beloved hymns were taken from pub tunes, right? Or, maybe you are aware that the masterful church organ was originally used in carnivals and was considered an instrument of sin.
Music was invented by God. All music. It is up to us to be excellent with it, in all of its forms. Granted, some people have used music to convey messages contrary to scripture and God's design for healthy relationships, as well as Satanic messages. But, being these folks don't know Jesus, this is to be expected.
There is nothing Biblical or even logical to support the idea of any style of music being of God or not of God. I have listened and been to the concerts of some bands that would make your hair stand up, but their lyrics clearly convey Biblical concepts, including the love of God and the importance of salvation.
Christian rock phenomenon? How old are you and how out of touch can you be? This has been going on for over 30 years, ever since old hippie rockers got saved and used their talents to minister via music.
Some of today's Christian metal bands are getting into arenas that people like you could not minister in. They often open and sometimes travel with secular bands - they don't change the message of their songs and even get some chances to preach a salvation message.
Be careful how you judge.
And obviously, Aladdinw has not heard of bands like Demon Hunter, August Burns Red, As I Lay Dying, Underoath, Flyleaf, and others. Boring - HAH!