Those who suffer with sexual sin carry a heavy burden of shame, and some have been wounded when they shared their struggles with the wrong person. Your purpose is to draw them out of isolation so they can get help and find freedom from sin. A red hot, scolding sermon on hell and damnation will drive them deeper into hiding, which is the opposite of what you want. Boldly speak all of the truth in love. Our approach with the sexually broken should be like Jesus’ when He restored Peter (who would have been greatly ashamed) after he’d failed miserably by denying Jesus three times. 

Brethren, even if anyone is caught in any trespass, you who are spiritual, restore such a one in a spirit of gentleness; each one looking to yourself, so that you too will not be tempted. Galatians 6:1

The following is a suggested outline for your message of hope. Sexual sin isn’t an appropriate subject for young children, so you may consider making an announcement 1-2 weeks prior that the topic is PG-13, and parents should have their little ones in Sunday school that day.

First, set the standard.
In a 2003 Barna survey, 28 percent of Christians said looking at pictures with nudity or sexually explicit behavior was morally acceptable. God’s standard, found in Matthew 5:28, is that lust in the heart is the same as committing adultery. The married man who uses porn is sinning against God – and is unfaithful to his wife. Christians aren’t immune from our culture’s “if it feels good do it” mentality, and those who’ve allowed this lie to influence their thinking need to hear God’s truth.

Show how destructive sexual sin is

“Just porn” takes out marriages and families; the tragedy is that most guys don’t realize it until it’s too late. At a 2003 meeting of the American Academy of Matrimonial Lawyers, two thirds of the 350 divorce lawyers who attended said Internet porn contributed to more than half of the divorce cases they handled. The aftershocks from porn addiction in a marriage are little different from the fallout from the physical act of adultery; there are many stories in Scripture that show the devastating consequences of sexual sin (such as Samson and David’s).