My comment to this article was:
Children should be protected from every sort of abuse. This includes enforcing laws against the forced marriages of underage girls to much older men. The last time I checked, such laws included young girls being forced into monogamous marriages with much older men, as well as the polygynous form of polygamy practiced by the FLDS.
In other words, the crime is the forced marriage and subsequent statutory rape of an underage child, not the form the marriage takes, which should be irrelevant.
If the FLDS practiced polygyny between fully consenting adults, I'd say to leave them alone, as I don't think it's the government's place to mandate what form a marriage should take, but only to assure that whatever form a marriage takes, that it's between fully consenting adults.
The welfare of children and the forms a marriage takes are two separate issues. Strictly enforce the former and disregard the latter.