Greg Mankiw points to an interesting, if slightly dyspeptic, essay on the puzzle of academic bias to the left. Thomas Reeves says it is mostly due to envy, aggravated by (relative) financial distress. Times are hard for scholars.
Serious economic problems face the glowing, self-confident scholar with little money. How, for example, is he able to find adequate housing? Even US$300,000, well beyond the reach of most young and many senior professors, won't buy much in Boston, New York, Los Angeles, New Orleans, Atlanta or Chicago, not to mention Madison, Sarasota, Ann Arbor, Palo Alto or Santa Barbara. The affluent suburbs, where the successful in other fields gather, are out of the question, of course. And so many of us move into older, deteriorating, often dangerous areas, telling all who listen that we made the choice deliberately and that we, being humanists, have a natural desire to live among the poor and oppressed. In my experience, some English and anthropology professors actually believe this nonsense, and enjoy dressing as factory workers and displaying furniture obviously purchased at a rummage sale.
In this talk from 1998, Robert Nozick put it down to a subtly different cause: a sense of frustrated entitlement. Intellectuals are trained to believe that the market has overthrown the proper allocation of reward according to merit. Note the difference: envy is wrong; insisting on reward by merit (however Utopian) is right.
The intellectual wants the whole society to be a school writ large, to be like the environment where he did so well and was so well appreciated. By incorporating standards of reward that are different from the wider society, the schools guarantee that some will experience downward mobility later. Those at the top of the school's hierarchy will feel entitled to a top position, not only in that micro-society but in the wider one, a society whose system they will resent when it fails to treat them according to their self-prescribed wants and entitlements. The school system thereby produces anti-capitalist feeling among intellectuals.
Of course, the two causes are not mutually exclusive.