I think true to freeper form, people here don't just buy what a person says no matter what side of the story they are on. I don't think its meant to be 'mean-spirited'. At least not all of them that question this dad and family. You seem quite quick to defend a person/a family you know nothing about. It certainly isn't out of the realm of possibilities that someone in the family is involved.
I work about two miles from the Smart home. I am acquainted with people who know them, and all say they are a really fine family. The little girl, Elizabeth, appears no different from the 14 year olds in my neighborhood ward, or local congregation. The majority are not worldly, by today's standards. Everyone in the neighborhood would know which kids that age would be likely to be boy crazy. It can't be hidden. Every ward has a well-run youth organization. Each young person has teachers and youth leaders who would be involved with that teenager -- and with that teenager's friends -- to a sufficient degree to know if she had any tendency toward trouble. I've held those positions myself, and the first thing you find out is which kids need extra help and guidance.
Everything I'm hearing from Elizabeth's young friends and extended family is that she is exactly as her parents have said.
Are there deep dark secrets in a few of the families who appear to be solid on the surface? Of course. But if there were anything like that going on here, word of it would have surfaced by now.
So, technically, you're right. I don't know these people. But everything I know about the environment, and everything I've heard from people who do know them tells me that they are innocent victims of some predator.