"Mormonism in the mid-eighteenth century was as weird and scary as Scientology, and Brigham Young was quite comparable to David Miscavige. They’ve mellowed quite a bit by the evolutionary process by which parasites do better if they don’t kill their hosts and evolve toward symbiosis."
That's somewhat true, but with the lack of a strong central government, with its modern investigation and enforcement powers, Brigham Young was able to abuse his people on a level that Miscavige can only dream of.
Indeed. If the US government had actually been able to enforce its laws far enough out into the frontier to reach Utah, I doubt the Morg would have survived Brigham Young.
Of course, having a strong law-enforcing government in the frontier would also make Westerns a whole lot less interesting.