Arnold Kling takes on the issue of why so many academics are leftists in his usual, clear, prescriptive manner. 

...Another way of describing political alignment is in terms of freedom and responsibility. How much freedom should people have to pursue their own interests and desires? How much responsibility should they have for their own well-being?

The conservative ideology favors individual responsibility. However, conservatives see a need to protect the culture from behavior that runs counter to conventional morals. In that sense, conservatives are willing to restrict freedom.

The left takes the opposite point of view. Modern liberals see no reason to restrict individual freedom. However, they view people with inadequate health care or education as victims who should not be held responsible for their condition. Instead, support for health care and education should come from those whom the left regards as villains, referred to as "the rich," or "corporate America," or "straight white males."

...When we see leftist ideology statistically predominant among college professors, news reporters, or open-source software advocates, what we are seeing is self selection. What Richard Florida dubbed The Creative Class is a self-selected group that seeks freedom without responsibility in their professional lives. Thus, we should not be surprised that their ideological bent is toward modern liberalism, which translates this personal preference into a political platform.

...Freedom Without Responsibility does not scale up to the level of society. As government takes over more responsibility from the individual, rewards start to accrue to the most ruthless and effective political operators. Work and production are crowded out by confiscation and bribery.

And, of course, folks of a libertarian ilk immediately recognize that removing responsibilities from one place (for ex., paying for your own healthcare) necessarily removes freedoms from others (increased taxes, choosing your own treatment, etc.).   Kling is a Good Man.