I just happened to stumble across this article (from about a year ago), which talks about the recidivism rate of inmates of Guantanamo Bay. That is to say, the number of inmates who then go on to join or return to militant activity.
It seems to me that given the gloriously wonderful conditions of Guantanamo Bay, it would be surprising if inmates didn’t rise up to fight against the oppressive Americans.
If the goal is to turn people against the US, you have certainly succeeded. Well done America!