Because we are fallen by nature, the fact that something is natural to us, the fact that we are born with it, is not a moral justification. Indeed, the fact that something is natural to natural-born sinners seems a good reason to suspect it, not support it.
If, for example, someone is born a pedophile or a sexual sociopath of some other sort, that fact is neither an exoneration nor an excuse to let their preferred activity proceed unabated, much less to endorse it with government protection. Sex is too important and too powerful a thing to leave to our fallen nature. It needs redemption too. It needs to be transformed and domesticated or else by it we will ruin ourselves and others. It takes only a moment to notice the pathetic litany of misery, betrayal, disease, guilt, conflict, and death that sex has scrawled across human history.
We all are born pagan, and our sexual desires, like everything else about us, desperately need the redemptive and transforming grace of God. It's not what we are born that is the measure of good and bad, but the things that God wills us to be once we are born again, the things into which He is re-creating us, that show us the direction we ought to go. The measure here is the mind and character of Christ, into whose image we are being transformed, and not what proclivities we have at birth. We are duty bound to stand with Him. When we see Him either endorse or practice things like homosexual activity and homosexual marriage, then we can endorse it too.
Until then, when it comes to sexual sin, we must tell ourselves and others what He told the woman caught in adultery: “Go and sin no more” (John 8: 11).
It won’t be easy to do, either in our own personal practice or in our address to others. But that is our obligation