Todd Zywicki, at Volokh Conspiracy discusses college intellectual diversity, and why it matters.
The purpose of education should be to teach students how to think, not what to think. I don't know how you can teach students to analyze arguments and determine the truth value about claims about the world if you don't expose them to a variety of ideas.
This is an excellent article which is related to the issues brought up in Brainwashing 101, which I reccomended in one of my previous posts.
(OOOPS - HT to the Instapundit, who else?)