Because the cult based on plural marriage has the last say regarding morality.
Your an idiot ....the Mormon religion is not based on plural mairrage .... in-fact, they haven’t even practiced it for 140 years ....
Is there a problem with the Christian religion also (of which the LDS Church is a part of) ...
Afterall ... God is the Father of Abraham, Isaac and Jacob .... two of the three confirmed polygamist!