Historically, marriage was created to establish a legal bond or contract of property ownership. Sometimes the property was just the woman, but typically marriage included the transfer of land, animals, money, or other material items. A woman was not a party in the contract, but the subject of the contract, meaning she was irrelevant in taking part of the terms of the contract. The woman’s opinion or love was not needed, nor wanted in most marriages.
As a society we have moved away from the marriage-as-a-contract concept; however, even today we still have men and women in the United States who cling to the misogynistic idea that a woman is property to serve and bear a man children. These men and their Stepford spouses cite the historical aspect of marriage as the justification for demeaning a human being (or allowing themselves to be demeaned.)
Gay marriage has only one purpose, the expression of love between two people. There is no property exchange and no issue of who is the master and who is subservient, (unless both parties agree to a 50 Shades of Gay-type relationship.) You can’t attach outdated expectations of a gender-based owner/property understanding to a marriage between two people who are of the same gender.
Perhaps now heterosexuals shed the mantle of the woman as property and confirm marriage a legitimate expression of love.