I think there's some indication that sexual sins are worse than others. This passage put special emphasis on them.
1 Cor 6:18 Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body.
19 Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own;
20 you were bought at a price. Therefore honour God with your body.
Sexual sin is against the Holy Spirit and you don't mess with the Spirit.
