Proverbs 27:5 Open rebuke is better than secret love.
The question is when? Is this for only certain people in your circle? Are there particular situations when this would apply? Is it okay after you have gone to a person several times privately, as Betnich stated was done on part of JVI.
An example of open rebuke: Mark 8: 31-33
31 And he began to teach them, that the Son of man must suffer many things, and be rejected of the elders, and of the chief priests, and scribes, and be killed, and after three days rise again.
32 And he spake that saying openly. And Peter took him, and began to rebuke him.
33 But when he had turned about and looked on his disciples, he rebuked Peter, saying, Get thee behind me, Satan: for thou savourest not the things that be of God, but the things that be of men.