I agree with you. Several months ago I listened to a lawyer who is an IP expert make the case on The Jason Stapleton Program that there is actually no such thing as IP (I'm sorry I don't have a link). I was fascinated by the discussion. Without trying to remember all the details of his arguments, he basically made the distinction between real (i.e. tangible) things versus abstractions like intellectual property.
Basically it comes down to the difference between theft and fraud. You can't steal someone's idea (like a song or story) that they voluntarily introduce into the public domain because those things aren't physical, or "real". But you can commit fraud (a violation of the NAP) by attempting to pass off someone else's work as your own.
Did it happen to be Stephan Kinsella? I was trying to search the show you mentioned, but it's not coming up. Stephan Kinsella is the only lawyer/anti-IP guy I know of though.
Edit: found the episode here. It was Stephan Kinsella. http://www.stitcher.com/podcast/stephan-kinsella/kinsella-on-liberty/e/kol196-the-jason-stapleton-program-intellectual-property-41036189
Yes that sounds right. Now I need to go back and listen to the show. It's good stuff.
Yeah, that's a distinction some people have a hard time with when they hear my argument. They don't realize that playing a Michael Jackson song at your rock show isn't the same thing as pretending to be Michael Jackson. Since Michael Jackson isn't performing and you are, you own the benefits of the performance in that venue. People wouldn't pay to come see you if you sucked at playing MJ's tunes.