Maybe instead of slamming him right into real music we should start him on rock genre songs that sound like country. Like Mama Said.
Maybe that slow song by Kid Rock.
Kind of like how drug dealers don't hook children on crack right away. They start them on weed first.
We can probably hook him on slow songs then slowly move him to real stuff like Metallica.
Who knows? Maybe a year from now you will have him headbanging to death metal.
Baby steps.