Martin Luther on polygamy
"I confess that I cannot forbid a person to marry several wives, for it does not contradict the Scripture. If a man wishes to marry more than one wife he should be asked whether he is satisfied in his conscience that he may do so in accordance with the word of God. In such a case the civil authority has nothing to do in the matter."
Unless the authority is the US, and you ex post facto Roman laws and customs to persecute a religion...
Did you only just find this? I think they quote this in Daniel Peterson's Offenders for a Word, and it also includes a Catholic quote thinking of it as a way to prevent the King Henry the VIII from getting divorced. If we are heretics for polygamy, some major Christian churches flirted with heresy.