Whaaaat?? They don't have anything to do with polygamy. Just ask them, they'll tell ya.
Until they actually disavow polygamy--say it was wrong, JS and BY were wrong, it was never sanctioned by God, it's not the order of heaven, it must be removed from scripture, and apologize to the victims of that practice, they will always be accused of having culpability in these crimes. Whether or not it's right to say they do, if they don't want to own it, they need to really disown it.