Think about it this way... is there any instance in the Bible where someone who has accepted Christ is called a "sinner"?
There's actually a different word used to describe Christians in the Bible... We are Saints.
That's because we are sanctified (set apart) because of what Jesus Christ has done for us. We are no longer of the world. We are not the same as the people who have not accepted Christ (sinners). We've been set apart and God has placed His seal on us.
We still battle with the flesh and we are capable of doing things that "miss the mark" (even adultry, etc). But when we do, because of the Righteousness of Christ, we are not 'charged' with that sin.
For example... say you live in a small town and the Judge has a son. That son is usually a pretty good kid but one day he messes up big time and gets in an accident while driving drunk. That son is guilty of driving drunk. But the judge, because He loves his son, and because his son is different than the regular hoodlums he sees, refuses to allow the prosecutor to bring charges against the son. He doesn't "see" the guilt of his son. The son realizes he messed up big time and gratefully accepts his father's mercy and grace and goes on to college and being a good man.
That's a loose analogy, but it's the way it is with us and God. We are His children. Factor into it that really, Christ has already served the sentence for our guilt... God isn't going to charge us with that sin.
No, God doesn't "wink" at it. He takes it seriously and He will discipline us when we need it. But He doesn't treat us the same way He treats the other "hoodlums" that are not His children.
We are set apart (sanctified), we're different now that we have Christ. Christ is what makes us different, let's not forget...it's not by our own effort.