"We don't really care about that. Go ahead, sue us and see how far you get..."
Could this be a deliberate strategy to test the GPL in a courtroom and defeat the FSF with superior legal firepower, invalidating or weakening the GPL? Such a strategy may be profitable to Sony, allowing them to make proprietary versions of GPLed software, building in trusted-client access-control technologies (something Sony is very keen on) without fear of their secrecy being compromised.