Here’s the key, I think: It’s because gay and lesbian people perceive Christianity as not just asking for a certain modification or a certain disciplining of their behavior but rather for a suppression or erasure of their identities. In modern Western cultures, being gay or lesbian—or bi, trans, queer, or some other parallel or related identity—is perceived as just that: an identity. It is not only a matter of performing or not performing some genital behavior; it’s rather that the behavior that Christians want to prohibit is seen as inextricably bound up with their personhood. And so, unlike Thomas Aquinas who treated homosexuality as just one particular permutation in the broader category of lust (Summa Theologiae IIa IIae Q.154, arts. 11-12), most of us in the West today think of homosexuality as a category of persons, rather than a category of actions. As Steve Holmes has commented (in a forthcoming collection of essays in honor of Stanley Grenz), “For the churches of the West, whatever formal stance they take concerning the ethics of human sexuality, there is (generally) an awareness, often acute, of the cruelty of imposing ethical norms that conflict with personal identities.”
And this, in turn, explains the huge investment conservative movements like the ERLC have in getting Christians like me to stop calling ourselves “gay.” The reason that’s important is that if my identity isn’t gay—if, on the contrary, I’m just another human person just like my straight neighbors—then it becomes easier to see why and how Christianity’s traditional prohibition of same-sex sexual behavior isn’t an intolerably cruel diminishment of my personhood. If I’m just a Christian—if there’s no basic identity difference between me and my “straight” Christian friends—then the same ethical norm (don’t have sex with people of the same sex) can apply to both of us equally without unfairly infringing on the basic identity of one, but not the other, of us.