The Authority by which We Proclaim

What right do Christians have telling anyone how to live their lives or why they should change the way they live? When we look back at the past and consider the atrocities that have been committed by Christians, how can we proclaim to the world Christ, and him crucified, when it is in the very name of Christ that so much evil has been perpetrated? Simply this: Our authority to proclaim the gospel is found in Christ and in his words, not in those who bear the name of Christ.