In The Name of Allaah, The Most Merciful, The Bestower of Mercy

Chapter: The prohibition of reviling the deceased without right or a legitimate (overriding) benefit  

The deceased—that is the deceased amongst the Muslims (i.e. in general they are not to be reviled).  As for a disbeliever there is no sanctity for him except if reviling him will harm those of his relatives who are alive, then he is not reviled.  And if there is no harm (in reviling him), then he has no sanctity and this is the meaning of the statement of the author [i.e. Imaam Nawawi]’’Without Right;’’  because we have a right to revile those dead disbelievers, who harmed the Muslims, fought against them and strove to corrupt their religion.

‘Or (without) a legitimate (overriding) benefit;’’ (i.e. not to revile the dead unless there is a legitimate overriding benefit in doing so); such as when this deceased person was a person of innovation and he has already disseminated it (i.e. his innovation) and disseminated it amongst the people, so here there is a benefit to revile him, warn against him and his path, so that the people are not mislead by him. [Sharh Riyaadus Saaliheen 6/230 of Imaam Muhammad Bin Saaleh Al-Uthaymeen] http://www.sahab.net/forums/index.php?showtopic=124263// <![CDATA