The OP of this thread is dealing with a growing trend on University campuses where students, often with the guidance of faculty,(that's teachers and stuff) are displaying more intolerance to the opinions of "non-liberal" voices. In support of this point several examples of prominent conservatives being shouted down and being forced to cancel speaking engagements were cited.
When asked for an example of a similar situation involving a prominent liberal receiving similar treatment the example of Eric Holder cancelling a speech to a group of police academy graduates was given. This example is not an apples to apples comparison for two reasons. First, it was a police academy. The OP was dealing with colleges and universities. Second and most important, it was an Oklahoma citizens group that organized the protest. It wasn't affiliated with the academy or the graduates.
So to sum up, in a thread about trends on college campuses a rebuttal was offered that didn't involve a university, students, or faculty. The only similarity is that he did cancel the speaking engagement due to protest.