I am not trying to point out a flaw or start an argument. Really, I am just curious. Luther and Melancthon both maintained that the monogamy limitation was unbiblical. It seems fairly straightforward to me. Polygyny is practiced widely throughout the Old Testament and is never condemned in either Testament that I know of.
So if the earliest Protestants recognized this, how did the standard denominations come to hold to strict monogamy?
So really it is two questions. How do they defend it today? And how did it historically develop from the time of Luther and Melancthon? (these two might have different answers)