The litmus test isn't about who is sinning or not, but as Kris points out, what the Christian does when convicted by the Spirit to quit sinning. If the Christian obeys the Spirit, then Jesus is the person's Lord. If the "Christian" continues to sin, claiming that they are under mercy and not to be judged, then they will go to hell: Jesus is not their Lord.
For sure, I have many sins. I was just telling my wife that the more I progress in Christ, the "more and more" he convicts me. I've struggled with some sins for a couple weeks, and others for years. Jesus is faithful to complete us, even if we are not faithful (because it's for His glory, not ours), so we can expect growth and spiritual fruit in those who hear his voice.
I think it's good to be civil. There's a man I know who would go to the altar of the church I went to, and cry out to the Lord to be saved. People would help him, comfort him, reach out to him. He had been gay for years and years -- it was a deeply-rooted stronghold for him and he could not shake it by himself. I'd sit with him at Starbucks and we'd talk and have a good time. But when the conversation turned to his sexual exploits, I had to rebuke him. I was there to help, but not to enable. Homosexuality is a sin, and not to be tolerated. So, we understood each other. I moved from the area, so don't know if the Word took root in his heart or if it was just a passing fad for him -- I didn't know if he would stick by his choice for Christ when it was tested -- but this didn't prohibit me from being civil to him. But it's a sin -- people who are practicing homosexuals and think nothing bad of it won't inherit the Kingdom.