Consenting adults who love one another and wish to marry should not be excluded from that institution just because they happened to be born gay.
Via Melissa at Shakesville:
After careful consideration, including a review of my recommendation, the President has concluded that given a number of factors, including a documented history of discrimination, classifications based on sexual orientation should be subject to a more heightened standard of scrutiny. The President has also concluded that Section 3 of DOMA [which defines marriage for federal purposes as only between a man and a woman], as applied to legally married same-sex couples, fails to meet that standard and is therefore unconstitutional. Given that conclusion, the President has instructed the Department not to defend the statute in such cases. I fully concur with the President's determination.
Consequently, the Department will not defend the constitutionality of Section 3 of DOMA as applied to same-sex married couples in the two cases filed in the Second Circuit.
—Eric H. Holder, Jr., Attorney General of the United States, in a statement regarding the Defense of Marriage Act's federal definition of marriage as only between a man and a woman, announcing that "this Administration will no longer assert its constitutionality in court."