This episode was NOT about the Mormon church. It was based on the "Fundamentalist Church of Jesus Christ of Latter Day Saints" and its leader Warren Jeffs. Jeffs is currently serving 10-life for various charges including sexual conduct with minors and incest. The REAL Mormon church has denounced him many times and often has mentioned their dislike of him trying to show any association with them.
That being said, I love how this show isn't afraid to tackle topics like this. What these young girls go through is terrible and TV can bring it to light sometimes better than print media can. It even lightly touched on the fact that many boys are put out of the compound because there aren't enough "wives" for everyone.