It's been out a while, but I appreciated the discussion of free speech in GMT 99. It's a complicated and touchy subject, but I think many of the points were spot on.
I think the key (that Jason and Bri correctly identified) is that everyone has a right not to be silenced through coercive means. Nobody has a duty to provide a platform for any particular person or speech, or to associate themselves with that speech or person.
Even if that's understood, it's hard to pinpoint exactly what's gone wrong in situations where someone's speech rights have been violated, but multiple parties are involved. For example, a university recently cancelled a speaking event due to riots. One might wish that the university had "stood up" for free speech on principle, and allowed the event to happen anyway. They might be applauded for doing so, but it wasn't their duty. There's no reason the university shouldn't act in its own self interest (to prevent further damage), or in the interest of the safety of its students. The rioters have violated free speech (and committed arson, vandalism, etc.). The university is not an accomplice, but another victim.
One might also argue that the university has a duty to expose its students to different points of view, but I don't think that's quite a free speech issue. It's a duty to the students, rather than to any particular speakers. And I think it could best be served by hosting civil debates, rather than giving equal airtime to speakers at different events.
With so much information available today, there are innumerable examples of efforts to silence offensive speech, especially because in many forums that speech seems to go unchallenged. I think in these types of situations it is important to be sympathetic, and try to imagine how we would feel depending on whether we strongly agreed or disagreed with the speech in question. Even then, it's often complicated, and I'm not sure how I feel about certain situations.