Not that I agree completely with what Bryan says, but I do admit that I do not wish to join an anti-PC crusade. I think that the real problem is that the academy has been dumbed down. PC is a symptom of that, but in and of itself PC is not particularly important. If professors were smarter, the worst parts of PC would go away.
I'm not saying that all smart professors are non-PC and all dumb professors are PC, but I'll bet that within the academy the correlation between IQ and willingness to listen to Larry Summers is strongly positive.
I would be willing to give 9-to-1 odds that fifty years ago a random sample of professors in liberal arts departments at top-50 universities would have had a higher average IQ than a random sample of Fortune 500 CEO's. Today, at even odds I might take the CEO's.
Fifty years ago, the pressures against free inquiry came from outside the academy. Today, they come from inside. When they do, my guess is that they come primarily from people who are dumber than the average faculty member of 50 years ago.
One of the signs of dumbing down is that professors cannot tell the difference between an argument and a person. So if you disagree with their position, they say, "You are trying to squelch me." But if they take away another person's right to speak, they think they are making a point.