I have read a few articles from the right wing recently complaining about the politicking of liberal professors. Until yesterday, I didn't really understand what the were getting at.
It makes sense to me to ground your teaching in real-world examples. If you're teaching a statistics class, then analyzing welfare statistics seems reasonable to me. If you're teaching biology, then debating the ins and outs of stem cell research seems entirely appropriate. Though they are common battlegrounds of today's political realm, as long as they tie in with the lesson, I think any controversy can be excused.
In my physics class, we are covering motion in two dimensions. Basically, ballistics. In a simple example involving range-finding, my professor segued into a review of the documentary Why We Fight and the Iraq War. He repeated a quote from the film regarding the success rate of so-called Smart Bombs and without much transition at all, stated that "we shouldn't be killing people."
It was an awkward moment, I thought, even though I happen to completely agree with him. I didn't see how the side note appreciably increased our understanding in any way, especially since Smart Bombs have on-board guidance systems and are not simply launched projectiles.
I have emailed him about the incident, and have yet to receive a reply.