If you are a Christian and you are on Facebook, eventually you will ask yourself this question: “how am I supposed to respond to my so-called friends who promote sin on their wall?”The examples are legion. Maybe one of your old friends from high school is clearly not following the Lord, and takes every opportunity to publicize exactly how drunk he got last night. Perhaps you are friends with someone from your church who “celebrates marriage equality” on his page. The most common example for me is people that I used to coach in soccer, whose lives (if Facebook is any indication) revolve around partying.Here are some principles I apply in dealing with this:   1) Don’t be the truth police.In some sense, many of these scenarios often fall under the heading of “someone is wrong on the internet, and I must do something about it!” Our lives are filled with enough actual relationships—and by actual, I mean people we know and talk to and see—that it just isn’t possible or wise to patrol Facebook for error. Remember the irony of the internet age: many of our friends are people we don’t even know. So don’t over react if you see the celebration of sin on-line.2) Unfollow people that glorify evil.If you are friends with people on-line, and their life is one that either causes you to stumble, or their content is just not glorifying to God, simply unfollow them. I’m not saying this as a word form the Lord (as it were), but simply as my advice. My presence on-line is designed for edification and encouragement. If I can’t open my Facebook page without being confronted with sin, then it stops being either edifying or encouraging to me.3) Consider how well you know the person.If a friend you haven’t seen in years posts that they are in favor of marriage equality, hitting their inbox on the proverbial head with Al Mohler links is probably not going to be effective. But if this is someone from your church, or someone that you actually know, then a conversation would be helpful.4) Be on the look-out for evangelistic opportunities.If a distant friend is going through a trial, I might message him, tell him I’m a believer, and ask if I can pray for him. I’ll follow that up by asking if I can call him, to hear how he is doing, and look for an opportunity to explain the gospel to him. If someone that I haven’t seen in a while seems to be drifting away, I’ll call them or message them. I don’t plan on confronting them (“exactly what kind of public place could you possibly have been that drunk in?”), but rather simply check in with them. With that said, I don’t pretend I haven’t seen what is on-line. If someone tells me that everything is fine, nothing is amiss, they are growing in their love for the Lord and memorizing Psalm 119—yet their on-line life seems to undercut that, I’ll ask about the discrepancy. Again, I’m not trying to be the truth police, but am simply trying to express genuine concern for them. After all, they are the ones that posted those pictures.5) I avoid all political arguments like an on-line plague.I just don’t want to burn any bridges to the gospel because I got into a debate with someone about what the most effective tax-rate is, or exactly what amount of guns it should be legal for a person to own. It’s better for me if I stay focused on the main thing, which is loving people and pointing them to Jesus.What about you? Are there any principles you apply in these scenarios?