To be fair to Stallman, he has always distinguished between "functional" works, such as technical manuals and encyclopedias, and works which express a specific

To be fair to Stallman, he has always distinguished between "functional" works, such as technical manuals and encyclopedias, and works which express a specific person's opinion. In the former case, Stallman believes that it's useful to modify works: You might want to update a technical manual for a new version of the software, or you might want to fix articles in the encyclopedia. But in the latter case, you're generally not inconvenienced by the fact that you can't edit someone's written opinions. So in these cases, Stallman tends to favor licenses which allow copying, but not modification.