Religious Scholars: 'Biblical' Marriage Not Strictly One Man, One Woman.
The debate about marriage equality often centers, however discretely, on an appeal to the Bible. Unfortunately, such appeals often reflect a lack of biblical literacy on the part of those who use that complex collection of texts as an authority to enact modern social policy.
As academic biblical scholars, we wish to clarify that the biblical texts do not support the frequent claim that marriage between one man and one woman is the only type of marriage deemed acceptable by the Bible’s authors.
The fact that marriage is not defined as only that between one man and one woman is reflected in the entry on “marriage” in the authoritative Eerdmans Dictionary of the Bible (2000): “Marriage is one expression of kinship family patterns in which typically a man and at least one woman cohabitate publicly and permanently as a basic social unit” (p. 861).
The phrase “at least one woman” recognizes that polygamy was not only allowed, but some polygamous biblical figures (e.g., Abraham, Jacob) were highly blessed. In 2 Samuel 12:8, the author says that it was God who gave David multiple wives: “I gave you your master’s house, and your master’s wives into your bosom. ... And if all this had been too little, I would have given you even more” (Revised Standard Version).
http://www.desmoinesregister.com/article/20130603/OPINION01/306030016/Iowa-View-1-man-1-woman-isn-t-the-Bible-s-only-marriage-view?gcheck=1&nclick_check=1
Now if they want to take the Bible literally let them, actually, I dare them.
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Believe it or not, I don't think I have ever seen that. 
