I wanted to offer a bit of advice to you, I've taken a lot of online courses and one I am currently in has religious overtones as well; it's a family/marriage course and people make comments like if you aren't the same religion you are doomed and things like that (not an predominately LDS area but religious nonetheless). I cringe every time I see it, but try not to overreact. The last one I responded to very politely using information directly out of the book. No reason for you to tone down or not discuss LDS history if you are being respectful. This LDS woman can respond all she wants; you should reply to her without emotion, with facts and you will be fine. Students who comment on discussions like they are on facebook typically get lower points anyhow. You should not hold back for her, you paid for the course and are contributing in the way the professor asked.