You've got your copyright laws confused. Traditional copyright law enables you to defeat copy protection schemes in order to legally excercise your right to "fair use".
DMCA criminalises ANY action (or any product) that may disable copy protection schemes.
For example, under the DMCA it is technically illegal to manufacture or sell marker pens in the US, because they can be used to defeat certain forms of CD audio copy protection, even though they have legitimate other uses.
(incidentally, CD audio copy protection inconveniences only legitimate purchasors of music. Case in point: I downloaded a pirate copy of the Foo Fighters new album. I burned a CD with the MP3s, and I could use them in a portable MP3 player etc. if I wished. I decided the album was worth buying, and so I did buy it. The legitimate CD won't play in my Amiga, because the copy protection causes the drive firmware to crash. More information here:
http://www.ukcdr.org/issues/cd/quick/ ).