Here is a followup from an email thread.
Here's a hypothetical conversation between two people:
A: "Do you listen to metal?"
B: "Yes"
A: "But metal isn't appropriate for a Christian."
B: "There are plenty of metal songs that are inappropriate for a Christian, and I don't listen to any of those, but some are good, and those I listen to."
A: "Why would you listen to metal if it has bad songs?"
B: "Every genre has bad songs."
A: "Not gospel music."
B: "What do you find offensive about offensive songs?"
A: "They condone things that God does not approve of."
B: "Do you think he approves of worship songs sung by people whose hearts are far from him? Do you think every gospel singer is sincere?"
A: "Well...no"
B: "Your gospel singers are no less sinners than my metal singers. The difference is that when the metal singers sing some of the few good songs, they aren't pretending to be disciples of Christ. This means they are able not just to sing powerful words, but that the spirit is able to accompany them, because they are sincere and not hypocrites."
A: "I find their songs offensive."
B: "God finds yours even more offensive. And while your offense is actually just the result of the imprint of false traditions from your religious upbringing, God's judgment is just and true."
A: "Well, I just wish they used more reverent music. The instruments they use and the way they sing aren't appropriate for worship."
B: "Do you think they sing your worship songs in heaven?"
A: "No, I'm sure they have better songs than that."
B: "How much better? God says his ways are so much higher than ours that they are like the distance between the heavens and the earth. Suppose you had the opportunity to hear the choirs of heaven. How much more vulgar would your worship sound than the relative difference between your worship songs and non-worship songs that happen to proclaim and celebrate the divine?"
A: "But we don't have the ability to sing like heavenly choirs. Our music is better than worldly songs. Should we all sing the holiest way we know?"
B: "In the Middle Ages, the Catholic priests deprived people from the opportunity to read the Bible because they said any language other than Latin was too vulgar for the holy writ. They even killed people who tried to translate the Bible into English. Do you think that was right?"
A: "Of course not. The people have a right to read the Bible in their own language."
B: "God thinks so, too. He always communicates to us in the words and figures we need to understand him as best we can."
A: "I don't understand what this has to do with music."
B: "You feel that your so-called worship music is the only form of music reverent enough to proclaim and celebrate the divine, but God teaches everyone in their own language. Shouldn't we want all people to hear and speak to God in the most sincere way they know? Isn't that more important than musical genres? Let's learn to value what God finds valuable, not just what the traditions of churches tell you is valuable."