WRONG. You eliminate the problem by ceasing the illegal behavior. Prosecution for statutory rape, bigamy, kidnapping, et al puts the current leadership behind bars and dissuades others from taking their place. You can still worship FLDS you just cant break the law.
Saying that you would prohibit the marital arrangements and other conventions of the FLDS while permitting its continuance is as much a legal fiction as was Catholic freedom in the Penal Law era in Ireland, even if there is no comparison between Catholicism and the FLDS in terms of theology, practice, or social structure. All that is fine. Would you then extend restrictions on the FLDS against other groups that are more dangerous to society, like Marxists, Islamic extremists, and militant sexual deviants?
I agree that laws against sexual abuse of minors should be enforced to the fullest extent possible. However, the individual crimes should be targeted, not a whole group.