'Four types of people are such that talking about them behind their backs is not considered backbiting: the immoral person who makes a public display of his immorality; the dishonest leader who, even if you were to be good to would not appreciate you and if you were to be bad to would hot forgive you; those who joke about their [and others'] mothers; and one who is a dissenter, who defames my community, and draws his sword against it.?