I watched a documentary on the history of heavy metal where Slayer's lead vocalist Tom Araya was interviewed. He's Catholic and he said that most of the band's persona was an image meant to scare people. In reality none of them are Satan worshipers and when he was asked if he thinks God Hates Us All he said no, it's just a cool sounding title. God doesn't hate us all.
The also write some songs that are religious in nature. Born of Fire, for instance sounds like it's a Devil worshiping song but the lyric Lost are those who trust a liar, Satan's son I'm born of fire suggest just the opposite.
I know Tom Araya is a Catholic, but he may have to answer one day for leading people astray who take their message seriously.