He's obviously not doing anything illegal, but something's off in the way he communicates with his wives. They're so subservient, so submissive. He's not a husband, he's a boss, a commander. He does not eat meat, so none of the wives and kids eat meat [so I wonder what if there's a health condition/situation in which eating meat would be necessary?]; he wants the wives to dress modestly, so they have to. They have to follow his orders.
I don't remember if this is something that was mentioned in the movie itself or I read it in one of the articles that were written when this documentary first came out, but he met each of his wives when they were going through a rough time. Those he met when they were teens, were very deeply disturbed teens. Adults - when they were going through a crisis or something. Now, this really smells fishy, because you can tell he's a smart guy, and I'm wondering if there weren't any manipulation, any kind of I'm-your-personal-savior thing. It's really easy to manipulate a young woman who's disturbed and very easy to make her believe he's "her man", and then she'll follow him anywhere. Of course, it's her choice whether to move in with him and have his babies, but you've got to wonder what he told them, because some of his wives completely turned their lives around to get into his commune.
And again - nothing illegal - just sort of make you feel icky.
As for the article you linked me to - it's legitimate for them to not want those kids in schools, but it's NOT legitimate to actually prevent the kids from going to school.