"How should I witness to a homosexual?"
Rather than offend homosexuals by directly confronting the issue of their sinful lifestyle, modern evangelism often tries to soften the approach by saying that "God hates the sin, but loves the sinner." This isn’t a new concept.
Charles Finney stated, "God is not angry merely against the sin abstracted from the sinner, but against the sinner himself. Some persons have labored hard to set up this ridiculous and absurd abstraction, and would fain make it appear that God is angry at sin, yet not at the sinner. He hates the theft, but loves the thief. He abhors adultery, but is pleased with the adulterer. Now this is supreme nonsense. The sin has no moral character apart from the sinner. The act is nothing apart from the actor. The very thing that God hates and disapproves is not the mere event—the thing done in distinction from the doer; but it is the doer himself. It grieves and displeases Him that a rational moral agent, under His government, should array himself against his own God and Father, against all that is right and just in the universe. This is the thing that offends God. The sinner himself is the direct and the only object of his anger."
So the Bible shows. God is angry with the wicked [Psalm 7:11], not with the abstract sin. If the wicked turn not, God will whet His sword—He has bent His bow and made it ready—not to shoot at the sin, but the sinner—the wicked man who has done the abominable thing. This is the only doctrine of either the Bible or of common sense on this subject" (The Guilt of Sin).
The biblical way to witness to a homosexual is not to argue with him about his lifestyle but to use the Law to bring the knowledge of sin. This will show him that he is guilty of breaking God’s holy Law, and he is damned not because of, but despite his sexual preference. The Law was made for homosexuals, as well as other lawbreakers. See Psalm 5:5 and 2 Peter 2:6–8 footnotes.