Here is a very nice, short video arguing against patent and copyright from learnliberty.org, by Dr. Stephen Davies, a Historian with the Institute of Economics Affairs.
Update: see also LearnLiberty: Can Artists Make Money Without Copyrights? (Video)
There are a few legal inaccuracies in the video, but they don’t affect the overall argument. But for example the video implies there are 3 types of IP rights—patent, copyright, and trademark—and omits others like trade secret and modern legislative innovation. It says that IP rights are limited in time, and gives as an example a 28-year patent and a trademark (the Coca-Cola mark). But patents last 20 years from issuance, not 28; and trademarks can be renewed indefinitely and trade secrets theoretically maintained forever. Still, this is a minor quibble.