Teachers are entitled to freedom in the classroom in discussing their subject, but they should be careful not to introduce into their teaching controversial matter which has no relation to their subject.
In other words, pontificating in the classroom about the issue of the day enjoys no legal protection given the influential AAUP definition of academic freedom--which is in the U.S. still the benchmark for the contractual and (in the case of public univeristies) constitutional protections. (In the UK, academic freedom is a statutory right, with some similarities to the AAUP provision; in Germany, it is a constitutional right, though one that does not encompass extramural speech, as the AAUP definition does.)
A university could, in principle and consistent with the AAUP standards, fire an instructor for dereliction of duties for using classtime to pontificate, even about wickedness. (Of course, various procedures would have to be followed before such a decision could be taken.)
But not all political references are forbidden. One can use examples drawn from contemporary events to illustrate topics that have a clear "relation to the subject." I recently discussed in a graduate seminar whether David Velleman (in a famous 1992 paper) was correct that no one could be alienated from having reasons for action--Trump, I suggested, might be a counter-example (maybe not, that was the main topic of discussion). So, too, per the linked article, discussing "lies" might make Trump-related examples quite relevant.
The main takeway, however, is this: being in front of a classroom is not a license, under academic freedom, to talk about whatever you want. Academic freedom as a legal right protects your disciplinary competence in both teaching and research. it is not a license to say whatever you want to a captive audience!