Run from sexual immorality! “Every sin a person can commit is outside the body.” On the contrary, the person who is sexually immoral sins against his own body.
Paul is clearly drawing a distinction between the sin of sexual immorality and every other sin. It would seem logical that he is pointing out that sexual immorality of all varieties is a ‘worse’ sin. In other words, in drawing a distinction, he seems to be saying that since sexual immorality is a sin against one’s very own self it is a more damaging, invasive sin. Paul also seems to confirm this in Romans 1.
Sin is not flat. There do appear to be some sins that are more damaging and have deeper effects than others. Sexual immorality in all it’s forms appears to be one of those as it violates the very dwelling of the Holy Spirit, His temple, our body.