Supporting the GPL but not copyright in general is actually a completely valid stance. The GPL is the inverse of copyright--copyright normally protects the rights of distributors at the expense of customers; the GPL protects the rights of customers at the "expense" of distributors (this is why commercial companies don't like GPL software). The fact that the GPL is based on copyright is incidental. In fact, I suspect many people who support the GPL would be happy if the rights it protected could be given to customers without relying on copyright; unfortunately, that is not the case right now.
It still rests on the assumption that content creators can set the terms for the use of their products. Something that is disregarded by the hacker community when it comes to films and music.
