Our culture suffers from an inability to distinguish right from wrong, good from evil, and whether or not good and evil are even real. Even among Christians you will often find an inability to articulate these distinctions and the reasons that we accept them. How can the world come to understand that there is objective truth, if we're shaky on it ourselves? The current state of affairs calls to mind Romans 10:14: "How then will they call on Him in whom they have not believed? How will they believe in Him whom they have not heard? And how will they hear without a preacher?" We have to understand that depravity is man's natural state, and that he tends toward it. It is the conduct of the church, which contradicts the law of love, that has created such confusion in the world. How can they even notice, much less put their faith in, a message that apparently does not even hold any meaning for those who purport to believe it.
In Ezekiel 44:23 the Lord speaks of His priests, saying: "And they shall teach my people the difference between the holy and the unholy, and cause them to discern between the unclean and the clean." Now, you might dismiss God's Word, saying to yourself, "Well, that's for the priests." The Lord has anticipated and answered your argument. In 1 Peter 2:9 He declares us to be "a chosen race, a royal priesthood, a holy nation, a people for God's own possession, so that you may proclaim the excellencies of Him who has called you out of darkness into His marvelous light..." Any other excuses?