The fact that the GPL uses copyright law is just an implementation detail. In practice, it really turns copyright on itself. In general, when somebody infringes

The fact that the GPL uses copyright law is just an implementation detail. In practice, it really turns copyright on itself. In general, when somebody infringes on a normal copyright, they are making some work more accessible. When somebody breaks the GPL, they are making some work less accessible, because all the GPL does is ensure that anyone can practically and legally modify and redistribute the software in question. If we imagine a copyright spectrum where the default copyright is x and public domain is 0, then the GPL is -x. So opposing copyright in general but supporting the GPL is actually an entirely consistent and rational position.