It gives the unbeliever a negative impression of Christianity.
How many people have had a negative impression about Christ and Christianity and ended up getting saved because God used it to reveal what's in their heart and drew them to Himself through His Son. My own pastor was such a man who thought Christians were a bunch of you know whats, lying deceitful hypocritical morons, because he was an agnostic agitator and couldn't stand them unless they could contribute something to his own stature and fleshy lifestyle. People have negative impressions about Christians all the time but it doesn't seem to hinder God from drawing people through His own lovingkindness.
Why should we be occupied with what the world thinks and says about Christians? Do we get disturbed when the world mocks and makes fun of believers? Do you people live in a cave, perhaps it's time that you come out of your hibernation and see the light of what's going on around you. No one is advocating that we practice being arrogant or hateful to our brothers or sisters in Christ or do despite to the Spirit of grace, for if we do God will deal with us as His children and discipline us and He knows just how to do it. Do you think that God is hindered or unable from saving the heart of the humble and contrite? Perhaps God would use the very thing that you are barking against to harden people's heart and make them bitter to eliminate their options and isolate them so that He can minister to them in that state and abase them.
Has David's adultery or Moses killing of a man or Paul's slaughtering of believers, that are all recorded in the scriptures for all to read, had a negative effect on people and kept them from being saved by mercy and grace? If it has hindered any, then why did God include them in His own inspired word? Lastly, have you ever considered the implication and application of when sin abounds...GRACE DOTH MUCH MORE ABOUND? Kind of mind blowing to think about, don't you think! Yes we are to edify, forgive, be kind to one another, love one another and minister grace to one another and we do that for Christ's sake and not for the sake of the world.