To be fair, their headline has a question mark in it (literally).
Meanwhile, over at Time Magazine, someone had apparently read the wikipedia article and followed up:
to the degree that they found a doc who'd discussed the issue with the group, which is/was worried about the problem, but does not believe it is genetic in nature.
To sum up: they kick out the boys, use corporal punishment to a degree considered unacceptable in the broader US community (even in the South), "marry" the girls off around puberty to men substantially older than them, definitely before the age of consent (which they may or may not even know about) and quite possibly even without whatever consent a teenager who has never seen anyone outside their small group could muster. And in some cases, overriding violent protest. As a result of this, they are suffering at a high and increasing rate of severe retardation in the resulting children who need constant care (which to their credit, they are doing a relatively good job providing). While they recognize _that_ is a problem, they've rejected all the generally accepted strategies for mitigating the problem (testing, avoiding reproduction between couples who share the gene, selective abortion, etc.).
I get that the ACLU is worried about constitutional rights being respected (altho this is really the last straw; they are so never getting any of my money). I get that a lot of parents immediately think, what if they took my kid? What if they court ordered me and my family to be DNA tested? and think slippery slope. But come on. The cases aren't exactly related.