If you have a wife and two mistresses and you all live together and you have children by all of them, that is perfectly legal. If you refer to the mistresses as “wives” that is a crime - bigamy. I think such laws violate the First Amendment because it is basically the speech, rather than the practice of polygamy or having multiple families, that is illegal.
Stat rape is a crime. I am not sure that rounding up the entire place is the best answer. The judge ordered ALL of the minors to be taken out. If my neighbor beats his kids, the state does not come and take all of the kids on the block. Legally, what is the distinction between my block and this awful Mormon cult? What if their cases get thrown out of court?
I suggest you read up on Warren Jeffs & his group. There have been tv shows on what goes on in those compounds. I have to go to bed or I would try to explain to you the difference between your neighborhood & this FLDS group.