> If you go to a lawyer for legal advice and then refuse to pay him saying "I haven't deprived you of a tangible product so it's not really stealing" you are missing the point, it's still theft.

That is theft because you've robbed the lawyer of his opportunity cost. For the time he was spending giving you legal advice, he could have been giving it to someone else that would pay him.

A more apt analogy would be secretly listening in on a lawyer giving legal advice to a paying client. You haven't taken anything away from him or the paying client, and all you've done is "copied" what was being heard anyway.