Well, GPL do prevent the production of an proprietary video player based on GPL code.
Sure, they can produce a video player full of spyware and then give the source of the spyware to their users, but then, that would render that spyware useless as soon a anti-virus got their hand on it. Not to mention, users would avoid the program as the spyware would then be known.
Your GPLed video player wouldn't stop that in the least. Were I a government in such a situation, I could very easily either claim sovereign immunity to any sort of copyright questioning, or I could write a function that monitors what files were opened by the user that used well-exposed file system APIs, like inotify. The GPL would not stop human rights abuses at all.
The nation-state might consider itself as above the law, but the contracted company who got the job to develop the player might think twice before breaking the law.
Or are we so jaded that we think every contracted company to the army, and every sub-contracted company being payed for a job by the NSA/CIA/FBI regularly go around and breaks laws because the think "hu, why not, my boss is the goverment, they wont mind!".
Sure, they can produce a video player full of spyware and then give the source of the spyware to their users, but then, that would render that spyware useless as soon a anti-virus got their hand on it. Not to mention, users would avoid the program as the spyware would then be known.