i had liberal professors who didnt hide it. i also had conservative professors who didnt hide it either. but i can honestly say that however their personal politics leaned, they were fair in letting opposing viewpoints be heard. the one thing they ALL had in common though, was a mentality of "dont just take my word for it" in nearly all my classes. doing research on both sides of an issue and making an informed decision for yourself was paramount and encouraged. i dunno how much i buy the "impressionable minds" part though. i dont think the kind of person who just blindly accepts everything their professor tells them is going to do very well in college.