Question: should faculty discuss politics in their classrooms, when it is unrelated to the course material?
Students at my University have told me that they have a simple rule for determining the political leanings of their professors: if the professor discusses politics in class, he is a liberal; if he doesn't discuss politics, he is a conservative. Is it unilateral disarmament for the conservative faculty to omit political discussion, or simply responsible pedagogy? I hold the latter view. I feel it is an abuse of the students' time and money to transform a multivariable calculus class into a political rant, and there is not enough time to have both an intelligent discussion of political issues and teach Stoke's theorem.
I have read studies that assert students leave college more conservative than they entered. I have read studies claiming they emerge more liberal. Conservative students who discuss these matters with me tell me that the bulk of the political indoctrination they receive in class consists (for the previous 8 years) of snide remarks about Bush, the stupidity of prominent conservatives, and standard leftist anti-American rants. Students who are influenced by such lowbrow fare are not likely to become great shapers of public opinion, and I suspect will conform to the opinions of their peers in their subsequent business and social spheres. So, I doubt there is much harm done.
In my early career, I did indulge in one minor bit of liberal bashing in my calculus classes. An important concept in physics is that of a conservative force. These forces are distinguished by the property that zero work is done by an object travelling in a closed loop when the object is acted on (only) by a conservative force. After defining this concept, I then dubbed nonconservative forces, liberal forces (not a conventional usage). I then would always observe that when subjected to a liberal force, you generally did work even when you went nowhere (net). Moreover, the most frequently encountered liberal forces, such as friction, work against you, no matter what direction you travel.
With mathematical political humor at this low level, I think it is clear that the propagation of conservative political principles is best served by my leaving politics out of my classroom.