The short answer is because the blood of someone else is on him

Douglas Wilson: A Planet Full of Sexual Pirates --

A commenter in the earlier post about Exodus International is checking to see if I am ashamed of Leviticus 20:13 yet, which I am not. ...

We know this, in part, because of the passage in Leviticus, and others like it. Backing away from such passages is backing away from a possibility of salvation for those trapped in same sex lust. The demand that we back away from this is a demand for us to stop loving homosexuals, and to start hating them. The homosexual movement, as it is playing out in America today, is a loud concerted demand that the church agree together that God’s revealed pattern of law and grace is not for homosexuals. Unbelievably, many quarters of the church are going along with it — withholding the gospel from homosexuals in the name of loving them.

Now what I have written above is the grand theme of the New Testament. It is all gospel, and that is what we were told to lead with. This message is what we are to use to tear down strongholds. When we do that, we may turn our attention to other lesser matters. So why needn’t the blood of a homosexual be upon him, as Leviticus says? The short answer is because the blood of someone else is on him.

... and the continuation: One of Those Circus Ponies