Watch Where You Point That Finger
Let's say you have a Christian friend who is not living according to Scripture. How close do you have to be to be able to bring up a situation in love EFFECTIVELY?!?! (I said "effectively" because some people are comfortable pointing out wrongs in anyone at any time and it makes them feel like they're doing God's work.) If and when the topic comes up, you better have A LOT of trust and love in the relationship bank...which is why Matthew 18:15 says, "If your brother or sister sins, go and point out their fault, just between the two of you. If they listen to you, you have won them over." Did you catch that?
BROTHER or SISTER...this connotes a serious, close, shared-blood and mission type relationship.
Don't be that Christian who loves to point out the sins or shortcomings of people you casually know. (No social media accusations, right?) At best, you'll be wasting your breath. At worst, you'll be creating rebellious hearts against the very word you're trying to lift up.
Rules of thumb for calling out anyone else's shortcomings...how close are you? If you're not in regular, supportive conversation, if you haven't eaten together lately, if you haven't prayed together...if you're not truly a brother or a sister in Christ, I suggest you can your criticism and leave it until you're in a better space to be effective. Unless you're in their immediate circle of trust and accountability--it's not your job, plain and simple.
Ultimately, the same Holy Spirit that worked in Bible times is alive and well today. You can be an echo, but let the Spirit take the first crack.