The abuses I see do not involve politics (yes, there's some indoctrination going on where I teach, but probably not a huge amount). Instead, the abuses I see focus on watering down the curriculum and coddling students—and giving high grades. (A good account of this is the book Generation X Goes To College.)
There are three reasons why students are treated this way.
One is political, there's pressure to admit poor students and make them succeed. Universities are of course heavily into "diversity," and often unqualified students are recruited. (There's a trend now to strengthen community colleges that would better serve such students. They've done that in my state.)
The second reason why students are coddled is because the university itself is under pressure to keep enrollments high—because the funding formula for the university is (typically) tied to enrollment. So faculty at such a school find themselves being constantly reminded to worry about "retention," and never reminded about academic standards, etc.
But the primary reason students are coddled is because if students are unhappy (as when a professor tries to set high standards), they will give the professor bad marks on the student evaluations of teaching. At a teaching institution, this is poison to a professor's career. (Typically, when a professor fails as a teacher, it is the intro courses that cause the problem. Many faculty went to ivy league or selective colleges in their own undergraduate days, and they have trouble adapting to schools with weak academic standards, particularly at the 100-level, where many students are unprepared due to open enrollment. The result is student complaints, and they lose their careers. I've seen this happen to several colleagues where I teach.)
Where this sort of thing happens the most is in the social sciences and in education. (It happens in the arts and letters too, but it turns out writing courses, which all students must take, are a primary reason why students drop out of college—many students cannot write to save their lives.) This is a matter of concern if not resentment in the natural sciences, whose faculty are well aware that they lose students to the the other discplines that grade easier.
The presence of Marxist politics and other substitutes for actual rigorous learning I view as more a symptom of a deeper problem, the collapse of intellectual standards.
Another symptom is the demise of the western civilization course. There is practically no college left in the US that makes its students take a simple, basic survey course of western civilization. Students instead end up taking odd hodgepodges of courses, with no unifying themes. They are required to "take two courses in 'historical investigation'," which can be a History of Feminism course plus a History of Popular Music course. Once I had a distinctly unsettling experience: I asked an undergraduate at my school if she knew when World War II happened. He had no idea (she didn't know it was [mostly] in the 1940s). This was an upper classman in biology. This is the real problem in universities today. Left-wing politics is only a symptom.
Well, this post has pretty much gotten out of control. Oh well.