How do we approach brothers and sisters in Christ who boast of their sin?
The answer is Jesus!! but what do I mean?
Jesus said His sheep hear His voice - that should be us!
Jesus said He is always with us and would never leave us - so you can talk to Him about anything!
Paul explained He took all thoughts captive to Jesus Christ!
Jesus said He did and said only what the Father told Him, and prayed we would be one with Him like He was one with the Father!
So the answer is always Jesus, meaning that when we have a question we need to ask Him!
Ok - lets give give some examples:
What church should you go to?
Answer - The church Jesus Christ tells you to go to!
What store should you go to?
Answer - The store Jesus Christ tell you to go to!
So - what do you do when you run across any sinner?
You ask the Lord your God how He wants it handled!
And guess what - you find out that all have sinned and fallen short of the glory of God - meaning you. All unrighteousness is sin, and since the right thing to do is to seek the Lord and listen to Him, we sin when we go to a church the Lord didn't ask us to. We sin when we try to handle a problem we see in another person without seeking the Lord, also.
In a nut shell - we are sinners in need of Jesus Christ. His mercy, grace, and forgiveness covers all that failing to seek Him and us doing that first! But that does not change what we should do! We should seek first the Kingdom of God, which includes the King of kings and Lord of lords - and He is call the Great I AM, and His name is called "The Word of God" (not our Bible but Him). So He is always with us and always willing to talk to us, but who is seeking Him?
There is a statement that goes - "If you have to ask"
We do have to ask Him, but if we are asking others what to do are we missing something.
Note: I am not saying we shouldn't get others thoughts also. He works through others. So maybe I seem a bit harsh on this, but others sin and so do we. Our problem often is that we see the speck in the other persons eye and miss the log jam in our own. And that is why we need to make it a habit of seeking Him, instead of a habit of worrying about the other person's sin. So, point everyone to Him, and what better thing can you do for them. If they listen and seek Him you have helped them. If they didn't, you at least gave them good advice that perhaps you too will listen to, because you know what the good advice is.