Argument: Bible condemns incest, supports its moral condemnation
"No one is to approach any close relative to have sexual relations. I am the Lord...Everyone who does any of these detestable things -- such persons must be cut off from their people" (Leviticus 18:6, 29).
"If a man sleeps with his father's wife...his daughter-in-law...a woman and her daughter...his sister, the daughter of either his father or his mother...it is a disgrace. They must be cut off before the eyes of their people...he will be held responsible" (Leviticus 20:11, 12, 14, 17).
"For John had said unto Herod, it is not lawful for you to have your brother's wife" (Mark 6:18).
"It is actually reported that there is sexual immorality among you, and of a kind that does not occur even among pagans: A man has his father's wife...hand this man over to Satan, so that the sinful nature may be destroyed and his spirit saved on the day of the Lord" (I Corinthians 5:1, 5).
"Rather, clothe yourselves with the Lord Jesus Christ, and do not think about how to gratify the desires of the sinful nature" (Romans 13:14).
"No temptation has seized you except what is common to man. And God is faithful; he will not let you be tempted beyond what you can bear. But when you are tempted, he will also provide a way out so that you can stand up under it" (I Corinthians 10:13).