If so, I would ask if he considers this casual copying illegal. Of course not. In the same way people consider print copying a casual act, an emerging generation of primarily young people consider music copying an equally casual an inoffensive act. Even if it did subtract value, you must admit it cannot be technically considered theft, not in the true sense of the word. In order for it to be logically considered theft, a CD, or studio master, or the compositions inside a musician's head, need to be deprived, taken away from its creator and owner.
Duplication leaves the original untouched.
In fact, it can be argued virtual duplication increases the value of the original - in much the same way radio play or movie soundtracks increase awareness and exposure to music and thus make it more valuable. The difference is, of course, the recording industry earns money through radio play and movie licensing, while it doesn't with the free trading of MP3 files. In essence, the free trading of MP3 files is about the loss of control and licensing income on the part of the recording industry - and not about broader ethical considerations. Music consumers resent being lectured to about thievery, especially from an industry with a track record of not only consumer abuse, but abuse and exploitation of artists as well. Unfortunately, the industry is far too monopolistic and atrophied to react effectively to the quick pace of change in both music technology and the Internet.