Interesting question.  An old friend of mine whom I’ve known since 4th grade and who has always been something of a Republican, recently asked me the same question.  There are two answers to the question:  (1) academics, especially those in the social sciences and humanities, are likely to be better informed than most and therefore are more sensitive to the injustices of the world;  (2) conservatives tend to be more sensitive to economic ambitions and are less likely to settle for the relatively low income possibilities in an academic life.  And then there are the religious bases for the conservative imagination, a state of mind less likely to find comfort in the inquiring approach to knowledge that characterizes most academic environments.