I think Jamie Raskin has it nailed.
He is professor of Constitutional Law at the American University's Washington College of Law and he testified on March 1, 2006 before the Maryland State Senate opposing a proposed anti-gay amendment that would stamp discrimination into that state's Constitution.
Senator Nancy Jacobs (R) posed this question at the end of his testimony:
"Mr. Raskin, my Bible says that marriage shall occur only between a man and a woman. What do you have to say about that?"To which he succinctly responded:
"Senator, when you took your oath of office, you placed your hand on the Bible and swore to uphold the Constitution. You didn't place your hand on the Constitution and swear to uphold the Bible."Please go and read his full testimony here. It's good. Hat tip to Andrew Sullivan and Wayne Besen.