Ephesians 5:11-14 (KJV)
5:11 And have no fellowship with the unfruitful works of darkness, but rather reprove them.
5:12 For it is a shame even to speak of those things which are done of them in secret.
5:13 But all things that are reproved are made manifest by the light: for whatsoever doth make manifest is light.
5:14 Wherefore he saith, Awake thou that sleepest, and arise from the dead, and Christ shall give thee light.

As Christians, we are to expose and reprove sin, whether it is in our own lives, in the church, or in the world. We can do this by living good, righteous lives, and also by speaking the truth in love.