Hmmmm. This is a good question I guess I will need to contemplate for awhile.
I really love all music - hard rock, soft rock, classical (I like the Baroque era/Bach), new age, jazz, religious hymns, contemporary, show tunes, and a little country.
But, that being said, I appreciate composition more than lyrics (consequently not a Bob Dylan fan), although you cannot be just one or the other. In fact, you could take most lyrics out and I would be happy.
You certainly have the right to censor some music but my opinion, better than censorship is to maybe take an interest in the music with him and ask him what he likes about this hard rock band (see if it is the lyrics or composition). If it is the composition, I wouldn’t be so worried. If it is the lyrics, and they are satanistic, or violent, then I would discuss it with him and how lyrics like that can damage the spirit. And give him other forms of music to pursue (Dilute the hard rock with something else)
Well, I have a confession - I listen to AC/DC (yup. I’ll put it on right after Bach or Fiddler on the Roof). They aren’t exactly the epitomy of Godly lyrics but I found the composition so attractive to my ears, when I am in a certain mood. Maybe I shouldn’t (I could certainly fast on AC/DC) and that’s what I’ll contemplate - maybe I’ll just give them up altogether.
Music is an interesting human endeavor. I beleive often at the level of creativity in our brain exists a darker side of us. Why God put it in us, I don’t know.