That's fine for justifying the ability to view and modify source code for your own use, but his definition of free extends to being able to freely redistribute it.
What's the difference between that and being allowed to sample or re-edit music and video and redistribute it?
He's only interested in the redistribution of source code, that is where his definition of free ends. Simply license the code so you can and the art so you can't and RMS is find and dandy with it. Tight controls on artwork to make money off of is good but tight control on source code is evil.
The closest he gets to extending out of his little bubble is that copyright should be 10 years only and then everything is public.
What's the difference between that and being allowed to sample or re-edit music and video and redistribute it?