Surah 49. Al-Hujurat, Ayah 11

The implication is that believers, whether men or women, shall never deride one another (Zamakhshari, Baydawi).

This applies no less to the faith of the one who insults than to that of the insulted (Razi): cf. 6:82 - "[those] who have not obscured their faith by wrongdoing".

Mutual ridicule ceases to be fun when there is arrogance or selfishness or malice behind it. We may laugh with people, to share in the happiness of life: we must never laugh at people in contempt or ridicule. In many things they may be better than ourselves!

Defamation may consist in speaking ill of others by the spoken or written word, or in acting in such a way as to suggest a charge against some person whom we are not in a position to judge. A cutting, biting remark or taunt of sarcasm is included in the word lamaza. An offensive nickname may amount to defamation, but in any case there is no point in using offensive nicknames, or names that suggest some real or fancied defect. They ill accord with the serious purpose which Muslims should have in life. For example, even if a man is lame, it is wrong to address him as "O lame one!" It causes him pain, and it is bad manners. So in the case of the rude remark, "the black man".