My school canceled a talk by a journalist from the Middle East last spring.
I was in the student union when I heard a professor arguing with the dean, saying 'we can't have someone who questions our foreign policy.' The talk got moved off campus to a coffee shop downtown, and only 15 people showed up. Do you think moving a speaker is the same as silencing them?
Man, I gotta push back on that a little. Moving them off campus still gave them a platform, just not a big auditorium. If the goal was to stop people from hearing the talk, letting it happen at a local coffee shop feels more like a compromise than a full on silencing. @ericschmidt hit on it, its not like they banned the person from speaking anywhere in town.