I understand, though I do not agree with it, the rationale for denying to a church its tax-exempt status if the pastor should turn his pulpit into a regular political soapbox. I'd like to note, though, that what applies to the occasional political objurgations of the minister must apply in spades to the constant, planned, and usually highly partisan political activities of teachers and professors.
Three things, moreover, make the politicizing of the lectern worse than that of the pulpit. First, the teacher has a captive audience, and has the power to make miserable the lives of those who dare to oppose his politics. Second, the teacher -- at a public school, or at any but a small handful of colleges -- is taking the taxpayer's money. Third, the preacher AS a preacher may in certain circumstances have a duty to urge his congregation to act in the world in ways that he deems to be required by their faith; but that is not the job of the teacher, who can claim no authority delegated to him from God, or from the state, for that matter.
I see that many of the departments and programs at my school are dedicated, as they themselves claim, to the producing of political activists. Why should Joe the Carpenter have to pay a single dollar toward the salaries of the professors? He does not have to pay a dollar toward the salaries of the heads of the DNC or the RNC ..
-Anthony EsolenH/T Leila Miller (via Nicole DeMille)