Many religions start off as cults, they are often underground groups that
are suppressed as threats to the religious/political establishment. But
over time they generally have the rough edges worn off as they become part
of the mainstream. You can see that with the Mormons, they've abandoned
some of their more troublesome beliefs over time, e.g. plural marriage,
blood atonement, the exclusion of black people from the priesthood and a
couple of others that seemed especially whacky or which caused political
difficulties. That's no different than Jews or Christians who generally
don't stone people to death these days or advocate slaughtering their
enemies right down to children and livestock. Of course once a religion
goes mainstream and sheds some of its goofier aspects there is usually a
backlash and you see the rise of fundamentalist splinter groups which return
to the old ways, and that's happened with Mormons, Jews, Christians and of
course Muslims. Ironic, isn't it, that it's these splinter groups who claim
to be closer to God who typically indulge in more odious behavior including
violence.