First of all, I see where you’re coming from in saying that this music cannot be Christian, however, if you’d try to look past assuming that Jesus has your personal musical biases and look at what the music is really saying.
Second, just because music is popular doesn’t mean it can’t be used to praise God. The anger and hate in this music is directed towards evil, not bringing praise to it. That doesn’t mean this band thinks they can kill demons. They are quite aware that they cannot. They are showing how much against Satan and his follower’s they are. Don’t blame one band for the errors of other bands who play similar music.
Third, I realize you believe that you’re standing up for Christ, but you actually are causing more dissension and hate than this music is. You are wrong to stubbornly assume that your personal musical tastes are God’s. You can’t know whether Jesus would smash this CD. You have no idea what the music in Heaven will be like. It could have many qualities in common with this music. It’s going to be too glorious for us to express to one another here on earth what it will be like, so there’s no way for you to know.
Finally, as it says in the Bible, you shouldn’t use your tongue to bless God and curse man. Just because this music has qualities in common with worldly music does not make it wrong. All forms of music have been used to praise man and not God. That doesn’t mean that it cannot be used to praise God. Unless God does not want us to listen to or play music at all, which cannot be the case if He gives us the ability to play it, and states His approval of it in His holy word.
Heavy metal music can be sinful, but all music can. That doesn’t mean that it always is. Pride, on the other hand, is always sinful. Please try to let go of it. God bless you.