Stallman does *not* tell people "not to use vi". He tells people "not to use
proprietary software". I believe his classic joke about vi is: "using a free
software implementation of vi is not a sin [like using proprietary software],
it is a penitence".
It really is more of a joke than anything else. Stallman designed the other
major text editor (GNU Emacs) because he did not like the way vi works. It is
a technical preference. Not a philosophical one (as far as we are talking
about two free software programs).
On the GNU website, you can actually find much humoristic material making fun
of Emacs and even a song giving ed as the answer to the editor's holy war.
As for Facebook, the software it uses does not matter to the user (who does
not, and should not, control Facebook's computing).
The FSF article is about privacy issues raised by Facebook (like the spying
buttons), its censorship (like not transmitting chat messages Facebook
dislikes), its collaboration with governmental spying agencies (which is now
obvious since the PRISM scandal). I agree it does not belong to the core of
the FSF speech (more that of the EFF). However, it definitely is about
freedom.
