I don't think this has been posted here yet. This story and its legal implications are making a splash in the US right now:
www.portsmouth-dailytimes.com/news/32807/professor-files-suit-against-ssu
Nicholas Meriwether, a philosophy professor, has filed suit against his employer, Shawnee State University in Portsmouth, Ohio. Because of his religious convictions, he feels unable to address a male student as "Miss."
When the student complained (reportedly becoming belligerent and stating "Then I guess that means I can call you a cunt!") the administration advised Meriwether to stop using titles entirely, and instead refer to all students by last name only. Meriwether wanted to retain titles for other students and refer to this student only by last name. The administration initially approved this course but when the student threatened to file a Title IX complaint, the university told Meriwether he must comply with the student's requested title. Meriwether proposed complying in class, but placing a disclaimer on his syllabus to note that he was doing so under compulsion and in conflict with his deeply held convictions. The university said this, too, would violate its non-discrimination policy.
An internal investigation found that Meriwether's "disparate treatment" of the student had created a hostile environment, and he was issued a written warning. He is still employed as a tenured professor.
Now, to me it seems weird that this guy wouldn't just use the title as a courtesy in class, or else switch to first names for everyone. He doesn't seem to have tried very hard to find a solution that wouldn't single this student out. Basically he sounds like kind of an a-hole.
Nevertheless, I think the university took a weird turn when they switched from trying to find a compromise to simply insisting Meriwether use "Miss" for this student and disciplining him when he did not comply (if that is actually how it happened). IANAL but it seems tricky to claim that one's employer can compel speech to which the employee objects strongly, at least in a country where a pharmacist can't be compelled to dispense a prescribed medication against which she has moral objections...