With social science courses, there's lots of opinions and perspectives. I think it's inevitable that the professor will lean one way or another, and I don't think having an opinion is bad insofar as you're overall fair about the class. One professor I knew taught in Introduction to Global Economies class, and 10 out of the 13 books he's basing his class lecture on are anti-capitalism books. Thankfully, he is a very nice guy and he has allowed his students to write papers disagreeing with his thesis, giving most of them A's insofar as they back up their thesis with sources. The problem, of course, is that most of the text of the class leans toward one viewpoint. In a 100-level introductory gen ed class, the goal is to usually give the students a breadth of different opinions. I think his class would have been great as a "The Problems of Capitalism" class as an elective for an economics major to take, in which that information is within the context of studying the pros and cons of numerous economic systems. But ultimately, even if what they are saying is true, professors should try to be as neutral as possible.