Mmmmm...
Personally I'd go for;
Dear Sirs,
Whilst the practises of polygamous followers of Joe Smith are not representative of members of the LDS (of Utah, Inc., ™, ®, ©, Pat. Pend., Intel Absent, MMX, Reynolds 531, and don't forget the ickle spirit babies) as regards marriage (or equality of black people come to mention it), both the (unrepresentative of the LDS) polygamous fundies and the (representative of the LDS) common-or-garden Mormon are, at the end of the day, in the deepest sympathy, and with the utmost regret and no desire to offend, whacked out cult follwers of yet-another-bloke-with-a-beard-who-says-he-talked-to-god-or-is-otherwise-a-channel-of-devine-wisdom, a rather long list including Noah, Abraham, Enoch, Moses, Jesus, Saul of Ephesus, John of Patmos (mushrooms anyone?) Mohammed, all the Seikh gurus (apart from the book), Zoraster, the founder of the Ba-hai, Charlels Taze Russell, Charles Manson, the Beatle's guru, that guy at Waco, and for all we know AGuest, ad nausium, for ever and ever, Darwin..
Their religious hierachy uses certain identifiable techniques to control the actions of its members including control of information and shunning. They are high control groups.
Please feel free to parody, lampoon, satarise and humiliate them. They have perpetual open season on their literalistic credulous asses. Even if one person who would have otherwise listened to a Mormon Missionary sends them away with a flea in their ear, even if one child raised a Mormon exercises their rights of self-determination, it will be well worth the offended dignity and boo-hoos of those your program rightly targets.
How about targeting Jehovah's Witnesses next? They don't have the salacious sexual aspect of niches of Mormonism, but they will let babies die for want of a simple medical procedure. Maybe following a Hospital Liaison Committee that serve a major hospital for a few months is a good idea. They are specially trained Elders in the group who help fellow believers die because of an inconsistent and impossibly chronologically flawed piece of literalism and second-guessing. It's got everything; sick babies, machines that go bleep (least, you hope they do), dashing doctors, spunky nurses, officious fools, confused and distraught parents. Add in the dysfuntional homelife you'll witness if you follow them home, and the 'Stepford Wives' angle and you will be shitting yourself with delight when you get to edit down your footahe.
Keep up the good work!
Yours faithfully
I don't know if I get my feelings across, what do you think?