I think we need to distinguish between the civil contract of Marriage and the religious sacrament of Matrimony.
Marriage was—and is—always all about property rights. Up until about one hundred years ago, it had to do with a man purchasing a woman from her father. In ancient times, the marriage contract would specify the bride price; or, if the woman came from a family of means, a dowry, which represented an amount the woman would inherit from her family. Since women were property, they couldn’t own property, so this amount was settled on the husband.
There were all sorts of provisions about the return of the dowry if the husband divorced her, if she proved not to be a virgin, or if she was barren. It also specified who the woman would become the property of if she survived her husband. The contract might also enumerate such details as how many other wives the man might have, her status and level of support should he take a second or third wife, and how concubines or slaves kept for sexual purposes (male and female) that the husband might own. The marriage contract also specified inheritance rights, so that a child born of a wife took precedence over the offspring of a concubine or a slave.
Today all that remains of this body of property law are the partnership aspects. Married people are considered one person under the law, each being jointly and severally liable for the debts of the other, and mutually obligated for the maintenance and upkeep of the other. There is also the distribution of property upon dissolution of the partnership, which includes inheritance.
The sacrament of matrimony, on the other hand, is administered after the signing of the marriage contract. And it is administered by the couple to each other. The priest is simply the chief witness. According to the Catholic Church, the union of man and woman was elevated to a sacrament by Jesus Christ, but this is a bit of revisionist history. The actual codification of the sacraments didn’t occur until 1563. Before then, couples could declare themselves married and live as husband and wife with or without ceremony. In the matrimonial vows, each partner declares that they are free to marry, they give themselves to one another and pledge lifelong fidelity.
Whether matrimony is between one man and one woman, or between members of the same sex, is a matter for the religion to decide, not the voters speaking through the state. In this respect, passing a law to ban same-sex marriages constitutes a denial of a religious sacrament. In other words, this is not only a denial of equal rights, this is people of one religious persuasion using the state to impose their beliefs on people of another religion. Apart from being flagrantly unAmerican by violating our constitutionally protected freedom of religion, it is also unChristian for one group of Christians to deny sacraments to another.