Agreed. Can we then arrest the Islamic extremists in Dearborn, Michigan, the Communists and left wing radicals in Madison, Ann Arbor, and Boston, the homosexuals in the Mission district of San Francisco and Key West, and dangerous, race baiting characters like Jeremiah Wright, Barack Obama's former pastor, or David Duke? You could reasonably make the argument that these people are far more dangerous to society than the FLDS and that their suppression would enhance the social order. The children of Islamic extremists, leftist radicals, and even liberals and black ghetto residents can arguably said to be brainwashed as well.
Excusing one sin because someone is sinning in another way is wrong. They all need to be addressed.