Intellectual property represents work, and should be protected at least as diligently as any other sort of property. Stealing music through an online file exchange system is no different, morally, than stealing a car. In both cases you are taking value, not engaging in a voluntary exchange. The key question is always the same: have you entered into an agreement with the owner, or their authorized representative? Is the exchange consensual between the parties?
You’ll often hear people say that Bill Gates has plenty of money when they copy Microsoft software without paying for it, or the same argument in regard to some pop star when they steal music. But if you believe in the principle of mutual consent than how much money the owner of intellectual property has is not relevant. In fact, the point is about you, not them. Is it only your action which you control, and only you can determine what transactions to engage in. What kind of person are you? What are the rules you live by? Either you are engaging in an exchange with mutual consent or you are not.