Should a professor of accounting or chemistry be fired for using up class time to sound off about homelessness or the war in Iraq? Yes!
There is no high moral principle that prevents it. What prevents it are tenure rules that have saddled so many colleges with so many self-indulgent prima donnas who seem to think that they are philosopher kings, when in fact they are often grossly ignorant or misinformed outside the narrow confines of their particular specialty.
Over the years, the notion of academic freedom has expanded beyond autonomy within one's academic field to faculty governance of colleges and universities in general. Thus professors decide whether the institution's endowment can be invested in companies or countries that are out of favor among the anointed, or whether students will be allowed to join fraternities or the Reserve Officers Training Corps.
There is nothing in specialized academic expertise which makes professors' opinions on issues outside their specialty any better than anyone else's opinions. In no other institution -- religious or secular, military or civilian -- are people who make decisions that shape the institution unable to be fired when those decisions lead to bad results.
The combination of tenure and academic self-governance is unique -- and explains much of the atmosphere of self-indulgence and irresponsibility on campus, of which Professor Ward Churchill is just one extreme example. Re-thinking confused notions of "academic freedom" is far more important than firing Professor Churchill and thereby turning a jackass into a martyr.