OK...let's see you tie polygamy being a requirement for salvation to "Historical and cultural perspective"!
Like THIS???
"Now if any of you will deny the plurality of wives, and continue to do so, I promise that you will be damned;
and I will go still further and say, take this revelation, or any other revelation that the Lord has given,
and deny it in your feelings, and I promise that you will be damned.
Brigham Young - JoD 3:266 (July 14, 1855)