I am an author, I tend to believe that I should be able to get paid for doing that work (and it is work, Eleanor, it's really hard work)...You think you're entitled to deny all of those people their rightful share of the work they do. I don't understand why you think that.
That's the core of his argument. He thinks that since he has been making a living this way for a long time, and it has worked out all right for everyone, his way is the right way and anything else is of dubious morals, because why would you want to deprive a good man of good work?
The discussion seems to be about whether the girl has a "right" to download or share his sheet music. In my opinion, she can do it, and that's that; should he have a "right" to stop her? He has not convinced me that there's any reason he should have that right.