Correct me if I'm wrong, but if Emacs was licensed under a more liberal license (MIT, BSD) such forks would still be possible. (Non-free forks would also be possible)
I think software like LLVM, PostgreSQL, Xorg, Hadoop, etc have shown that you don't need a radical copyleft to push forward free software. You need something better than exists elsewhere, and this kind of behavior from Stallman holds back free software out of fear of bogeymen.
I side with camp which thinks copyleft is major way to push towards free software.
It comes down to wether you ideologically support idea that software should essentially be distributed with the source code always. (RMS's view).