Nicholas Kristof, himself a progressive, castigates the intolerance of his fellow progressives when it comes to conservatives and their ideas.
From Nicholas Kristof, A Confession of Liberal Intolerance – The New York Times:
Kristof goes on to document the phenomenon by citing several studies of bias in academia, making the point that a diversity of ideas is the most important kind of diversity on campus and that these narrow minded attitudes, such as the arrogant and easily-shot-down assumption that conservatives are not intelligent and have nothing to offer, squelch genuine education.