Paradoxically, direct attacks on academic freedom often come from within the university. There is a mood of intolerance towards those who hold unconventional, unpopular opinions, especially in the area of politics. Some academics do not simply challenge views that they dislike; they often seek to ban them and to prevent individuals who advocate them from working or speaking on their campus.I agree. I saw some of the same when I was in a graduate English program at an American university in the mid 1990s. Threats to academic freedom often come from the inside, not from an outside force. I believe the outside pressure being put on Ward Churchill in Colorado is actually a departure from the norm. Most often, those (students or faculty) who do not toe the academic line in the university feel pressure from the inside to conform or to move on.
In higher education, you don't need to worry about the government suppressing your opinions and curtailing your speech. Your fellow professors and grad students will do that nicely.