Where a professor marks your paper either up or down based on agreement with his political ideas, then he ought immediately to be taken to task, personally by you and then if that doesn't ammeliorate the problem, with his/her department head, or above. That is anywhere and anytime. Of course, it ought to apply (intellectually) to a discussion, say, on abortion at a Christian university. You should write this event up, carefully and accurately with full details and file a report.
Such student activism would certainly make the student feel better should she prevail and receive her pound of flesh. She would also have a reputation on that campus that would not further her education.
But how do you know this will be the consequence if you haven't tried it? It is NOT a consequence I ever witnessed. In fact, something quite the opposite was the case...students who demonstrated independence of mind and courage of speech gain the affinity of educators far moreso than do those who merely sit there and play the "I must get a 3.5 GPA and thinking/learning isn't much important." If to you, "furthering your education" means merely a job at the end, then you'll likely get exactly the education furthering you wish for. Not much.