I think you are referring to Deuteronomy 25:5-10. Here are the first two verses.
"If brothers are living together and one of them dies without a son, his widow must not marry outside the family. Her husband's borther shall take her and marry her and fulfill the duty of a mother-in-law to her."
I see no indication there that polygamy is ordered by God. The marital state of the "brother" in question is not mentioned at all.
The text is very clear that the requirment to take your brother's wife was enacted specifically to ensure the genetic survival of the twelve tribes of Israel, when God's kingdom people were decided by race and covenant. Now God's kingdom is decided by covenant only. There is no racial component. So even if you wanted to claim that God ordered polygamy in the OT (which I do not), I would contend that this passage could not be understood today in the same context.
Consider Leviticus 18:18 - "Do not take your wife's sister as a rival wife and have sexual relations with her while your wife is living." Finally, simply consider that God "made them male and female" and in the original order of creation there was only two.
Zack,
You know there is a lot of infighting on Free Republic between the Catholics/Orthodox and the Reformed/Protestants, and I am as guilty of it as anyone. However, when I see what this guy writes, I realize that it is to the detriment of all of us. The single greatest threat to Christianity is the "moral relativism" espoused by secular humanists. C.S. Lewis warned of this fifty years ago and it is close to destroying society's morality.
For what it's worth, I tend to avoid debate with idiots such as this one.
In Christ,
Rob