I don't know who Dan Lawton is, but he has an excellent article in the Christian Science Monitor on the dearth of political diversity in academia.
The saddest thing about an article like this is how many on the left--particularly those within academia itself--will simply act as the professors in his article did: dismissive and offended by the very notion of listening someone who disagrees with them politically ("Her opinion isn't even worth listening to. After all, she's conservative").
At my first weekend at the University of Chicago, the yearly "Aims of Education" address was given by the president at the time, Don Randel. There were many passages that contained such blatantly left-wing statements that afterward, at the traditional 'discussion' of the address (in which one faculty member pairs with one house of a dorm and leads the conversation), Professor Allen Sanderson (econ) asked the question: how many of you are voting for President Bush in November, and how many of you are voting for Senator Kerry (this was in fall 2004)? Three out of 54(ish) people raised their hands to say they were planning to vote for President Bush.
Why isn't there more diversity in the academic world? he asked. It was an excellent question and remains so today.
The fact is, if you are liberal, you will likely a) not notice that your campus is hostile to conservative thought and b) not really care much if it is anyway, since you agree with that. The problem, however, is that it ultimately harms the entire functioning of a university. What has made the Western educative tradition so manifestly superb was its commitment to free, open, and uninhibited debate. Our political systems reflect that fundamental value. Ideas are meant to be discussed, and no matter how much you may disagree with an idea, you have no right to silence that idea. Instead, you are encouraged to meet it on its merits and either support it or reject it based on articulated reasoning. That no longer exists on university campuses, where it is unquestioned truth that America is a fundamentally unjust society, capitalism is fundamentally unjust, Karl Marx has been given a bad rep, religion (and Christianity in particular) are the causes of the greatest human calamities and are only believed by fools, etc.
Those of us who have been through an elite, liberal school and are willing to take an honest look know that it's an issue. Free inquiry must be maintained at all costs, no matter how difficult or unpleasant it may be for professors to have to meet conservative arguments on their merits, instead of with crude distortions that are only acceptable inside their ivory bubbles.