The Free Software Foundation has been remarkably good at endorsing things that deny users' freedom. Encouraging people to make their software unmodifiable is well in line with them withdrawing support for distributions like Debian that make it easy for the user to choose to use non-free software.
On the other hand, GNU manuals with immutable rants about funding free software (such that you cannot use even a sentence or a diagram from the manual in another free work, according to the license, without copying the rant) are fully free.
I'm proud to use a distribution (Debian) that's not afraid to have its own set of free software guidelines and call out FSF's for being dumb. I think it's dangerous, as we see here with OpenMoko, for the community to passively accept the FSF's leadership role, because it means that newcomers to the community won't think critically about what the FSF tells them is freedom. (Another good example is the FSF legitimizing copyright assignment.)