What is the ruling in Sharia on using words like "animal," "donkey," "stupid," or "despicable" to describe a person?

It is not permissible to insult or revile a Muslim with any derogatory term, such as: animal, donkey, stupid, or despicable, due to what has been authentically reported from the Prophet (peace be upon him): "Insulting a Muslim is a transgression, and fighting him is disbelief." It is permissible for a Muslim to retaliate against an insult in kind, unless the insult involves an accusation of disbelief or a lie, in which case it is not permissible to retaliate in kind.