I make very sure that my political opinions do not surface in class. It is called professionalism. Professors are in positions of power. To use that power to advocate for partisan political outcomes makes a professor unprofessional and thus deserving of being fired.
I'm going to have to disagree here. While I don't think that trying to convert students' politics is a wise or successful form of teaching, I also don't think that it is an offense that should lead to firing, especially at the beginning of one's career. Most of the more fiery colleagues I've known have learned to be more flexible, to present things a bit more objectively and with much more humor as the years pass and the intensity of grad school and the quest for tenure eases up.
I believe that professors should not grade a student based on that student's politics; someone who does that repeatedly is behaving unprofessionally and probably should leave the classroom. However, presenting one's opinions, particularly if they are relevant to the course (which seems to be the case for the OP), can be effective and important. Ideally, presenting opposing points of view is the best approach, but that's sometimes unviable (i.e. I wouldn't present the views of holocaust deniers in a course on Jewish literature).