Keep in mind that when GNU/FSF say "free software," they really mean it's the software that's free, in an "Information wants to be free" sense. The software's freedom necessarily confers some liberties to you as well, but they still feel that software whose freedom can be taken away has a lesser quality of freedom than software that is guaranteed free forever. (You'd probably say the same about people — if your freedom can easily be abridged, it's worth less than inalienable freedom.)
That's not the sense I get from their manifestos. They seem to come more from a "freedom of end users to modify/share the software they receive" perspective, not the more cyberpunk information-wants-to-be-free perspective. The reason they like copyleft is because it makes it harder for a user's freedom to modify/share any software they receive to be restricted somewhere down the line: you're guaranteeing that not only are your immediate users given that freedom, but so are any indirect users of your software, via any derivative-works path.
