He has a right to be a dick, but that doesn't mean increased commercial success.
To me, this is the point. He has a right to be a dick. It's music he has written, and under the law he has control over who copies it. He is trying to stop people - by asking, not DRMing - from copying his work, without his permission, which is what he has, under the law.
His personal justifications or thought processes -
but that doesn't mean increased commercial success.
- are his own, too, and your belief in the correctness, legitimacy, or defensibility of those personal justifications has no affect on his right to control, under the law, how his music is copied.
I agree with the composer entirely in this case. If this young girl doesn't want to follow the rules, set by the composer as is his right under the law, then she can go and write the music she wants to perform herself. What's stopping her? Just that immature attitude toward the law that she has?
[And if she doesn't like the law, then she can do something about that too - study law, and work to have the laws changed. Welcome to what's called "civilization", with all its processes and structures... it's the main reason you exist today. Without it the world population wouldn't be what it is, and you wouldn't have been born, by a massive likelihood.]