If they relocated to a country where groups like them run rampant they will most likely end up dead, which perhaps unfortunately they know - don't think the world would hurt losing some people to their own medicine. Also there's nowhere in the world they will be happy, these people have extreme...
They probably stay here because we're one of the only countries that would let them get away with it. Children are protected from physical and mental abuse, but I think that should also include brainwashing and anything thats going to ruin the kids chance of a normal happy life like this...