Going back to John 4:1-27 we read the encounter of Jesus and the adulterous Samaritan woman by the well. Jesus did not offer salvation there just like a cup of water. Instead, He addressed the sinfulness of the woman which would show her need for salvation. He pointed out that she has had five ex-husbands and now she is cohabiting with a man who is not her husband. I guess that before her encounter with Jesus, the adulterous woman by the well thought what she did was not wrong. Many sinners tend to think that what they do is not wrong. But this encounter had changed her like it changed Rahab from a prostitute to becoming the mother of Boaz, the second mother-in-law of Ruth, the great-great grandmother of David and became part of the Messianic lineage. When the Gospel is preached, it will always intervene with the sin of people because it shows people their sin. In proper Gospel preaching, there is no soulwinning without telling people that they are sinners and why they are sinners.
The testimony of true converts always has this theme, "I am now saved by my Lord Jesus Christ, I do not want to sin anymore." Whenever there are people getting saved we see sin disappear. We do not see people sin all they want. Instead, we read 1 Corinthians 6:11 shows that how many immoral people were delivered from their unrighteous living to righteous living. They were washed, redeemed and set apart from the rest of the world by the Holy Spirit. Not only does intervention with sin happen during the preaching process but all throughout the life of the believer. There is no way that the believer can live like the rest of the world even if they are not sinlessly perfect (Titus 2:11-14).