I generally agree with Steve that there's nothing wrong with courses that present a subjective point of view, so long as the professor grades all students fairly and without regard to whether the student agrees or disagrees with the professor. I do, however, believe that there should be truth in advertising so that a course titled, "Introduction to American Politics," it should offer a survey of various political and methodological perspectives. If such a course presented only one perspective then it should let potential students know that with a title like "Conservative Perspectives on American Politics" or "A Socialist Critique of American Politics."
I also think that if a professor decides to present a particular ideological point of view, they should not be surprised if they are criticized for it. Too many academics act like hothouse flowers when someone takes them to task for the statements they make. Academic freedom allows faculty members the freedom to speak and teach about controversial subjects, but it doesn't mean that they are immune from criticism for doing so. Freedom of speech goes both ways. In my own case, I've gotten a fair amount of heat for things that I've written. In particular, David Horowitz once wrote that a statement I made was "anti-American, anti-white, and astoundingly ignorant." Strong words (though I should add that he has since retracted them). Some academics view criticisms like this as an effort to stifle them and create a chilling climate for those with unpopular views. My view was, to quote John Kerry, "Bring it on!" My views are certainly subject to criticism and if I didn't want criticism, I shouldn't have said them in the first place.
I also agree with Steve that the ideal situation would be ideological pluralism across the whole of academia and that making every class at every college relentlessly even-handed would be a terrible thing. Students should have the choice of picking schools that are extremely liberal, conservative, moderate, or any other viewpoint. At those schools that don't profess an ideology (a category that includes most schools) they should make every effort to bring about ideological diversity. In fact, I'm less opposed to taking affirmative steps in this area than is Steve. Much of what Horowitz and others have done is to using the diversity rationale that applies to racial or ethnic minorities and ask why it shouldn't also apply to religious and political conservatives. I, for one, can't think of why it shouldn't. So while I strongly support measures to increse the numbers of women and minorities in academia, also suppport measures to increase the presence of religious and political minorities. If nothing else, it wouldn't be a bad thing for faculty on hiring committees to say, "Gee, we all pretty much agree politically, so wouldn't it be good for us and our students to get a different point of view once in awhile." Such steps probably wouldn't completely overcome the self-selection process that tilts academics to the left, but it would help.
I think this is an important issue because academics are becoming increasingly distant from the society in which they operate. To some extent, this is inevitable (the ivory tower) and probably a good thing (critical reflection requires some distance and perspective). But only to an extent. When departments have partisan ratios of 9 or 10:1 and when academics inadequately address differing political views, they risk alienating the people who provide them with the resources necessary to do their jobs--students, parents, trustees, state legislatures, etc.--and provoking a backlash.
P.S. If any of my colleagues read this, please, please make sure that I never serve on another committee.
P.P.S. If any of my students read this, I'm still not changing your grade.