Oh, and Q, I don't find it particularly odd to hear people sing versions of Silent Night (Stille Nacht), whether they are Christian or not.   A lot of people enjoy hearing and/or singing the song just as art (music), regardless of their religion.   (E.g., both Neil Diamond and Barbra Streisand have Christmas albums.) And a lot of Christians enjoy hearing or singing songs from other religious traditions (e.g., Judaism, Hinduism) as well.