if you spent as much time studying history as you do posting comments, you could answer that question yourself.
Whether I agree with their religious beliefs regarding plural marriage or not, it does sound to me as if they were fleeing due to that aspect of their beliefs being made illegal. So, they fit the definition of refugee. But persecution? They came back, and laws forbidding polygamy were not repealed.
The answer is quite simple.
Those fleeing the US in order to escape criminal charges are fugitives, not refugees.