For the record, I study with a very devout Christian. The class includes atheists, Pagans, Mormons, Muslims, Jews, Catholics and Protestants. Everyone is a grown-up. Nobody uses it as a soapbox, least of all the teacher. That's the way it should be. People do say "Merry Christmas", "Good Yom Tov" and "Eid Mubarak" to students of the appropriate religions on holidays because it's polite.