If spotify is silently operating a P2P client, even when it's not being directly used, then that's an issue for people with bandwidth restrictions. It's trivial to get distracted by something, forget an application is running when you leave the house, and end up using much more bandwidth than you intended. It's worse still that as bandwidth increases, usage limits don't stay proportional. You suddenly have the ability to share faster, reaching your limit sooner.
As I said, I agree that the statement is hyperbolic, but I don't consider the issue trivial.