A couple of major distinctions: 1. the problem with Al Arian was never what he taught in his "place of business". The sort of garbage he spouted continues to exist in virtually every "Middle Eastern Studies" department in virtually any university. The problem was with the opinions he expressed in editorials and such outside of the classroom.
2. You are not a university professor (I am assuming) with tenure, which is a contract that explicitly forbids firing you simply for your opinions. The purpose of that is to allow free expression of academics, which, as with all liberties, allows both the good and the evil to speak out.
3. Firing people for differences of opinion as to appropriate expression is perfectly acceptable in an everyday business (or at least ought to be, although I wager many a frivolous lawsuit has been waged). It is not acceptable in university, where freedom of inquiry and speech is supposed to be the central principle.
I guarantee you that whatever minority of professors like Al Arian that would actually express opinions that are reprehensible enough for leftist administrations to fire them, far more conservative and simply unconventional (ie not flamingly left wing) professors would be out on their asses if the tenure system or something like it did not exist. I don't even want to think of what that would do to conservative students.