Thank you darrennewman. That worked perfectly.
Any idea why this version of the Pidgin Facebook Support is not on the repos at the moment?

Just so other users in the same situation as I was would know:

-I had no libfacebookarm-***.so file in /usr/lib/pidgin/ (so I had nothing to remove at the first place)
-However I first removed Pidgin Facebook Support from the Application Manager
-You need to be root to copy the new file to /usr/lib/pidgin/