Barack Obama's decision to have Pastor Rick Warren deliver the invocation at his inauguration next month has provoked anguish among some of his formerly ardent supporters. Joe Solmonese, president of the Human Rights Campaign, upbraided the president-elect according to The Politico. "Your invitation to Reverend Rick Warren to deliver the invocation at your inauguration is a genuine blow to LGBT Americans. (W)e feel a deep level of disrespect when one of architects and promoters of an anti-gay agenda is given the prominence and the pulpit of your historic nomination." Washington Post columnist Richard Cohen accused Obama of condoning a man who "dehumanizes" homosexuals. NPR talk show host Diane Rehm called some of Warren's comments on gays "ugly."

What had Warren done to provoke such feelings? He supported California's Proposition 8, which overturned a state Supreme Court ruling in favor of gay marriage. But wait, Barack Obama opposed gay marriage, didn't he? He stated explicitly during the campaign that he believed marriage to be the union "between one man and one woman." His supporters clearly assumed he was being disingenuous. Based on Obama's other beliefs, the atmospherics of the campaign, and their own hopes, they dismissed his opposition to gay marriage.

Other supporters of traditional marriage don't get such gentle treatment from proponents of gay marriage. Instead, as the above quotes on Warren demonstrate, there is a pretty systematic effort to portray opponents of gay marriage as simple bigots, no more deserving of respect than racists or anti-Semites. What particularly outraged gay rights activists was a comment Warren made in a TV interview when he compared two homosexuals getting married to a brother marrying a sister or an adult marrying a child. Those were not the most felicitous comparisons and probably unnecessarily hurt the feelings of gays and lesbians.

And yet, the point Warren was making was a valid one. Once you abandon the traditional definition of marriage to suit the feelings on an interest group, by what principle do you stop redefining marriage? Gays and lesbians argue that their same sex unions are loving, committed relationships. Fine. But there are, or could be, other loving, committed relationships involving more than two people. Supporters of gay marriage say this is a ridiculous slippery slope argument.

But consider the name that many gay activists have adopted. You no longer see gay and lesbian alone. Instead, the new terminology is LGBT -- lesbian, gay, bisexual, and transgender. Lesbians and gays say that without gay marriage, they cannot fully express themselves as they really are. But what about bisexuals? I ask this not to poke fun or to hurt anyone's feelings, but in all seriousness. How does gay marriage help a bisexual? I assume that if you are bisexual, you believe that you need to have sexual relationships with both men and women. If you are a bisexual man married to a woman, don't you need to break the marriage bond to express your bisexuality? If you choose to express just the homosexual side of your bisexuality, then aren't you gay? Likewise, if you choose to express only the heterosexual side, how are you a bisexual? Why is bisexuality not a recipe for infidelity? As for transgender people who believe that they are "assigned" to the wrong sex, their sexuality seems a deeply complicated matter. According to Wikipedia, the term "transgender," which is always evolving, today encompasses "many overlapping categories -- these include cross-dresser (CD); transvestite (TV); androgynes; genderqueer; people who live cross-gender; drag kings; and drag queens; and, frequently, transsexual (TS)." We are now in the realm of a multitude of sexual deviances.

Where do you draw a line? Once traditional marriage -- supported by centuries of civilization and the major Western religions -- is undermined in the name of love, there is no logical or principled reason to forbid polygamy, polyandry, or even incest. Gay activists recoil from incest. But on what grounds exactly? Suppose, after we formalize gay marriage, two 25-year-old sterile (to remove the health of offspring argument) twins wish to marry? Let's suppose they are loving and committed. What is the objection? That it offends custom and tradition? That it offends God? Isn't that just bigotry?

When asked which was a greater threat to marriage, divorce or gay marriage, Rick Warren laughed and replied that it was a no-brainer -- divorce. He was right. But there are very solid reasons to oppose any redefinition of marriage -- and it isn't bigoted to say so.