Indeed, if they are truly forced. They may have evolved to that with the latest, and now deposed, "prophet". But as I said on a earlier post, I've seen reports that they were arranged, but not forced. Of course, as in other societies with arranged marriages, parents can be pretty persuasive.
And of course any religion is no excuse for violating the statute law..provided the law in question is itself not violation Constitutionally guaranteed freedom religion. That is certainly not the case with underage "marriages" and sex with children.
At this point, from all I've read on the subject, this cult (religion?) is guilty of some very unsavory practices, using "religion" as an excuse. Aside from the indoctrination and control of children, their polygamous (more accurately "polygynist") lifestyle is against the law.