The primary purpose of marriage as a social and legal institution is to promote an ideal family structure for raising children. Same-sex couples (who are not able to have children that are biologically related to both parents) could never fit this model of the ideal family, so in order to argue for a right of same-sex couples to marry, one must appeal to other reasons, such as love between spouses. To publicly define marriage to be for the benefit of spouses over children is to loose sight of the reason societies created the institution in the first place.
Therefore, we should not allow same-sex couples to