[As an aside, he always thought it was interesting that his name was Charles Willis Manson. He claimed it should be read as: Charles' will is Man's Son, meaning that whatever he wanted to do was the equivalent of the Son of Man]
Fortunately, again, for us skeptics, these local cults grew up under the eye of history, and in the blaze of publicity. Any argument that christians use for their early church can be tested against the early churches of the Mormons, Millerites and descendants: Jehovah's Witnesses and Seventh Day Adventists, Christian Scientists, and some of the really modern ones like Hare Krishna and Scientology.
Christians like to argue that Jesus must be either Lord, Liar or Lunatic. Either he was an outright fraud, crazy, or we have to accept that he was the Messiah. Same arguments, however, apply to Joseph Smith: Prophet, Prevaricator or Paranoid. Many early Mormons were martyred for their religion, so what? Many cared enough about it to abandon their homes and move across the ocean to settle an unknown frontier, so what? They also claim numerous miracles, such as the sea gulls saving the crops from locusts, claim that no one else recognized the potential of the Utah region, and many so ons; so what?
The funniest recent example of US religious crankery is the Urantia Book. I have just reviewed Martin Gardner's book on it for FI. A copy of the UB is probably in your local library. Twice as thick as the Bible, in more ways than one, it is truly hilarious to read.
Anyway, you don't have to speculate what future Mansonites might do, just look at contemporary Mormons, JWs, Christian Scientists, or 7th Day Adventists, to see a likely analogy for the early christian church.
-- To know that the Bible is the literature of a barbarous people, to know that it is uninspired, to be certain that the supernatural does not and cannot exist--all this is but the beginning of wisdom.--Robert G. Ingersoll / Greg Erwin, VP, Humanist Association of Canada