that nothing is greater than the foundation upon which it is builtWhat about the Judeo-Christianity foundation? Didn't Abraham himself take a younger wife and didn't he just about kill his own son until some Angel showed up? To me it's not the past, it's what it is now.
God tolerated the taking of concubines. He never commanded it and there is no evidence that it was ever God's will for a man to have multiple wives. Polygamy was never a doctrine of Judaism nor was it claimed to have been divinely inspired as was the case with Joseph Smith. And if you read some of the Old Testament stories of men with multiple wives, there was always trouble as a result, more evidence that it wasn't God's will, but man's (doubtless influenced by the cultures in which he was immersed).
By their fruits ye shall know them. (Matthew 7:16)