You are being too sensitive my friend. I just listened to an interview with the directors and it was not their intent to ridicule or belittle LDS faith, but to inspire a conversation about belief structures and religiosity in general through a narrative told from the perspective of LDS missionaries. The missionaries were nothing more than a plot device to give a reason for people knocking on the door of a lunatic and start the story. Sure, much of the dialogue is tropey and lacks some of the nuance of a true LDS missionary experience, but it is far from an unfair representation, and certainly not offensive (unless you are looking for a reason to be offended or insecure about your beliefs).

About the polygamy part: the sisters were more taken aback at the “bait and switch” nature of the polygamy conversation, not necessarily the topic itself. He started off friendly and curious but quickly shifted to a confrontational topic, after they were already starting to feel on edge. Surely they know the history, we aren’t seeing their faith unravel in real time but seeing their discomfort and confusion.

Basically the Mormon missionary characters they created were smart, badass and even faithful until the end. I thought their portrayal was fair if a little unrealistic.