While I don't have a strong opinion on the subject, I do think it's important to keep in mind that the debate should be about getting closer to truth, not about who's right and who's wrong.
Ephesians 4:15 "Instead, speaking the truth in love, we will in all things grow up into him who is the Head, that is, Christ."
It's not judgmental to speak the truth, but it has to do be done out of love. I know that's not always easy, more often than not it's very hard, but it is what we should do.
I can see both sides here. I personally don't enjoy metal, or death metal and I can't reason in my head how death metal would be effective as Christian music. That said, I like the alternative rock genre, and some argue that that is "worldly" and morally incorrect. So it's an interesting topic and a worthwhile one, but try and keep it about bringing each other closer to Christ otherwise it ends up like most debates where one persons goes off one way and the other their way, without anything solved for the better.