It does seem rather ironic that this all took place at UC-Berkeley: the very home of the free-speech movement (1964-65).
Evidently, however, liberals believe strongly in free speech--just as long as it is limited to themselves, and their fellow liberals.
But that begs the question: Why?
It is really not that difficult to answer.
Progressives (a.k.a. liberals) believe in the natural progression of philosophical thought. Given this assumption, therefore, conservatives are not merely wrong; they are actually illegitimate, as they stand as impediments to this "natural progression."
We conservatives, on the other hand, simply see liberals as being wrong.
I suppose it does make some sort of sense--twisted, though it may be--for liberals to reject the legitimacy of us "impediments" to their posited utopia...