It's well known within a certain rather narrow community of people. The folks who booked him may just have read his name on a list of "vaguely important people who are willing to give speeches".
If your university hired someone who only spoke Mongolian but spit in people's faces when they extended their hand for a handshake, would you be upset at the speaker or the idiot who hired him?
RMS lacks basic social graces. He preaches to the choir but somehow still manages to piss them off with pedantic shit like GNU/Linux. Why doesn't he just copyright it so he can plaster the GNU logo all over everything and be done with it.
"If your university hired someone who only spoke Mongolian but spit in people's faces when they extended their hand for a handshake, would you be upset at the speaker or the idiot who hired him?"
If their spitting was common knowledge, as RMS's eccentricities are, then yes. Of course I would be upset primary with whoever booked them...