Throwing missionaries to the wolves on this without traiing... Ouch. Bad mistake.
It occurs to me that this isn't too different than any question a Christian would potentially have to face. "If God told you to sacrifice your son to him right now, would you prepare to kill him for real? If not, why not? God has done that."
The difference is that because this is so much more recent, Joseph Smith can't be pushed away as some strange person from some different time period who's maybe just part of a lesson and not a real living human being, and it's a new question, not part of old, old gospel. Smith was not too far removed from us and our world and our laws, so it's fresh and painful and more real.