Is it permissible to gloat over someone who gloats over me?

It is not permissible to respond to gloating with gloating, because it is among the reprehensible morals, and its display is forbidden due to the Prophet's (peace and blessings be upon him) saying: "Do not express gloating at your brother, lest Allah have mercy on him and afflict you." However, joy and gloating are permissible if they are for the sake of stopping the harm of the gloater and cutting off his mischief. What is forbidden is the display of gloating; as for its mere occurrence in the heart without display, a person is not held accountable for it.