Stanford Professor Keith Humphreys writing at The Reality-Based Community:

What we really know from the P.C. anecdotes that are being published is that at least some academics are feeling threatened and silenced. But we don’t know that this is happening any more now than at any other time in history, nor that it’s truly a national phenomenon rather than a feature of a subset of universities (Or maybe even a subset of schools within a subset of universities). So enough with the anecdotes and on to systematic surveys of faculty and students that will reveal whether we truly face a educational crisis or are just panicking over a few negative, unrepresentative experiences.

Exactly.

See, also, Dan Drezner.