I think this is why the debatable proposition that samples used in hip-hop and mashups need to be cleared with the copyright holder (rather than being fair use) has never been decided by the Supreme Court. Nobody ever sued Girl Talk over it, because if he fought back there was a risk that the existing pro-copyright decisions like https://en.wikipedia.org/wiki/Bridgeport_Music,_Inc._v._Dime... would be overruled.