In some departments, I can at least understand the argument that most professors will be liberal because nearly everyone in the field is liberal. But this is not true of economics, and the disparity there is strong evidence of systemic hiring bias at the university.
Some of it could be limited by who applies as the private sector will pay better if you are actually good at the job.
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.
“In some departments, I can at least understand the argument that most professors will be liberal because nearly everyone in the field is liberal.”
You hit the nail on the head here - look at the departments he was including, they were ones like journalism or sociology where liberalism is very prevalent. I’d bet this student would find a lot more Republicans if he included math or science departments (if said student can even find the math and science departments). Out of all the classes I’ve taken, which are largely math, science and engineering classes with an occasional humanities credit, I’ve only had one professor who was even mentioned their political beliefs, and that was in a philosophy class.