There is absolutely no causality here. None. Ideology has nothing to do with the subject matter per se. There is nothing in journalism, economics, or sociology that implies liberal or conservative viewpoint. In fact, only unanswered questions leave any room for viewpoints. Consider Walter Kronkite, who finally conceded that (to wit) "of course we [journalists] are all liberals. What else are we supposed to feel when we are surrounded by hunger..." One could recited a long, long list of statistics --- starting with the doubling of the life span in the past century --- that demonstrate how good capitalism is for the poor. Even after the recent calamities, the value of America assets is twelve times greater than in 1982 -- a remarkable result. One has to be blind to these truths and selective to what he chooses to see to arrive at "hunger" etc.
More recently, our troops have opened scores of schools and hospitals in Iraq. One could not miss them upon arriving to Iraq. But have you EVER seen that reported? There is nothing in the doctrines of journalism that dictates one to close one's eyes. If a journalist does so it is purely his/her choice.
Maybe not, but think about who wants to go study sociology? Gender studies? Even for other subjects, where the current academic debate is not 100% liberal, I think it's natural that liberals will be more attracted to the career. I suspect smart conservatives are more naturally inclined to use their talents in the private sector, which, after all, their ideology actually respects, while for smart liberals it seems there is no higher calling than academia.
But especially in the case of certain subjects, I just can't see most conservatives being too attracted to them.