One of the many compelling reasons to oppose the WIPO broadcast treaty in its current form is that it wraps another layer of property rights around works that are broadcast. The problems this causes become far clearer when works in the public domain are involved.
Imagine an old Charlie Chaplin movie in the public domain. Anyone has the right to view it, copy it, distribute it, or play it in public. The movie belongs to all of us, Chaplin and his affiliates long since compensated by its sales while it was subject to copyright law.
Under the proposed WIPO broadcast treaty, a TV network that took this public domain movie and played it over the air would have the right to sue anyone who taped the movie off of that broadcast and redistributed it.
Compare this to what happens when a book falls into the public domain. The text is available for anyone to read, copy, distribute, or adapt. If a publisher decides to print some copied of the work and sell them, anyone who acquires a copy can copy, distribute, or adapt the text from that new printing. It doesn't matter that the publisher has invested money in finding a previous copy of the work, or spent money on the paper and bindings. Those costs, presumably, are offset by the price the publisher charges for the book itself. The fact that others can subsequently copy the book is just part of the calculus that a publisher has to make when putting a public domain work into print.
Broadcasters, when asked why they need an additional IP right in the signal, often talk about the investment they make in finding the programming, arranging and scheduling it. There are also the costs of just running a station–the infrastructure that lets the broadcast be seen. But the broadcasters make back all those costs when they sell advertising–the same way they make money no matter where the content comes from. It's also worth noting that broadcasters didn't have to pay for their slice of the airwaves they send signals over. Part of that deal was that the broadcasters must contribute to the public good. And that's not what's happening when they press for additional rights to lock down content that belongs to the public.
The point of the public domain is to give everyone the right to access and enjoy the work after its creator has been fairly compensated. The lack of restrictions on public domain works serve to increase the spread of those pieces of art that are our common cultural heritage. When broadcasters say that the individuals can't distribute their home tapes of Charlie Chaplin, but must instead hunt through film archives for a print they can copy, the broadcasters are frustrating the goal of spreading works in the public domain. Creating new barriers to access certainly isn't promoting the progress of the arts, which is the entire point of copyright law.
Those who broadcast video and audio recordings aren't creating creative content, any more than those who print and ship books do. They are providing a channel to distribute that content, just like those who print books or produce CDs and DVDs. They certainly have a right to make a business (and, as it seems, a lucrative one) out of that distribution. But having a hand in getting the content from the producer to the consumer doesn't entitle them to ownership of that content, whether taped off of their signal or transferred from a fragile celluloid print onto a computer.