David Boies sums up the case he and Ted Olson are making in favor of a constitutional right to gay marriage:
Countries as Catholic as Spain, as different as Sweden and South Africa, and as near as Canada have embraced gay and lesbian marriage without any noticeable effect — except the increase in human happiness and social stability that comes from permitting people to marry for love. Several states — including Connecticut, Iowa, Maine, Massachusetts, New Hampshire and Vermont — have individually repealed their bans on same-sex marriage as inconsistent with a decent respect for human rights and a rational view of the communal value of marriage for all individuals. But basic constitutional rights cannot depend on the willingness of the electorate in any given state to end discrimination. If we were prepared to consign minority rights to a majority vote, there would be no need for a constitution.
The ban on same-sex marriages written into the California Constitution by a 52% vote in favor of Proposition 8 is the residue of centuries of figurative and literal gay-bashing. California allows same-sex domestic partnerships that, as interpreted by the California Supreme Court, provide virtually all of the economic rights of marriage. So the ban on permitting gay and lesbian couples to actually marry is simply an attempt by the state to stigmatize a segment of its population that commits no offense other than falling in love with a disapproved partner, and asks no more of the state than to be treated equally with all other citizens. In 2003 the United States Supreme Court in Lawrence v. Texas held that states could not constitutionally outlaw consensual homosexual activity. As Justice Anthony Kennedy elegantly wrote rejecting the notion that a history of discrimination might trump constitutional rights, “Times can blind us to certain truths and later generations can see that laws once thought necessary and proper in fact serve only to oppress. As the Constitution endures, persons in every generation can invoke its principles in their own search for greater freedom.”
There are those who sincerely believe that homosexuality is inconsistent with their religion — and the First Amendment guarantees their freedom of belief. However, the same First Amendment, as well as the Due Process and Equal Protection clauses, preclude the enshrinement of their religious-based disapproval in state law.