Though I am more sympathetic to the argument that important ideas be aired than to the argument that they should sometimes be suppressed, I think it is a debate we need to have. Whether we like it or not, science has a habit of turning up discomfiting thoughts, and the Internet has a habit of blowing their cover.
Tragically, there are few signs that the debates will happen in the place where we might most expect it: academia. Though academics owe the extraordinary perquisite of tenure to the ideal of encouraging free inquiry and the evaluation of unpopular ideas, all too often academics are the first to try to quash them. The most famous recent example is the outburst of fury and disinformation that resulted when Harvard president Lawrence Summers gave a measured analysis of the multiple causes of women's underrepresentation in science and math departments in elite universities and tentatively broached the possibility that discrimination and hidden barriers were not the only cause.
But intolerance of unpopular ideas among academics is an old story. Books like Morton Hunt's The New Know-Nothings and Alan Kors and Harvey Silverglate's The Shadow University have depressingly shown that universities cannot be counted on to defend the rights of their own heretics and that it's often the court system or the press that has to drag them into policies of tolerance.
The freedom to ask and attempt to answer questions that others may not approve of is at the heart of academic freedom. I have always taken it for granted that tenure would increase academic freedom, and assumed that the recent controversies over the issue, such as the comments of Summers and Churchill, were isolated events. But if Pinker's interpretation of Hunt, Kors and Silverglate is correct (I have not yet read them), then they were not exceptions to the rule of academic freedom, but indicative of a general tendency within the academy to "quash" the academic freedom of anyone they disagree with. If such a tendency exists, then tenure is not the guarantee of academic freedom that it is made out to be, which seriously undermines one of the strongest arguments in favor of tenure.