Speak not evil one of another, brethren. He that speaketh evil of his brother, and judgeth his brother, speaketh evil of the law, and judgeth the law: but if thou judge the law, thou art not a doer of the law, but a judge. There is one lawgiver, who is able to save and to destroy: who art thou that judgest another?
What law is being spoken of here? The new law Christ gave--to love one another. If we speak evil against our brother, we are not demonstrating love. It is not up to us to destroy a brother's reputation. God is judge and will deal with him accordingly. We are to love, not give final judgement.