The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
If the legality of the raid in in question, it may do more harm than good in the long run -- even if we presume they're guilty. The state may have to presume they're innocent until proven guilty, but you don't have to! However, even if you've already mentally convicted them, remember that the police aren't supposed to make exceptions on the Bill of Rights, even for cases where "everybody knows" who the bad guys are.
Now if you're outraged that I would suggest such a thing in a case where innocent children are probably being forced into incestuous marriages, please leave your comment on MSP (FLDS Polygamy: Good solutions? Bad solutions?), and not here (just to keep the discussion grouped).
As you may have noticed, next segment of my novel is about Mormon fundamentalists. This wasn't timed to coincide with the latest news -- the scheduling of the serialization was planned months ago, and the book written years ago -- but it might provide some insights on the subject. As I explained in the note on the polygamy sub-plot, part of my intention here was to shed some light on the complex relationship between mainstream Mormons and polygamy.