Lady Gaga’s mega-hit song “Born this Way” sold millions of copies affirming what many people believe: homosexuality is hardwired. In fact, people think that’s as axiomatic as saying the earth revolves around the sun. No rational person rejects the idea. The only hold-outs, it is said, are either ignorant of science, homophobic, or bigots (read: Christians). But before I explain why this view is beset with problems, let me make a tactical suggestion. Many Christians get defensive when someone says homosexuality is inborn. I understand the temptation to argue against this claim. But it’s a mistake to try to show...