There are “two grounds” for refraining from loving him. The first is that he performed no righteous deeds that would warrant loving him, and thus remained merely one of the kings who wielded power. Loving particular individuals of this kind is not religiously prescribed. This ground, together with the position of those who do not consider his sinfulness established, rests on believing that he acted on an interpretation.
The second is that his conduct, including the affairs of al-Husayn and the people of al-Harra, involved deeds indicating his injustice and sinfulness.
As for the scholars who cursed him, such as Abū al-Faraj ibn al-Jawzī, Ilkiyā al-Harrāsī, and others, they did so because of the deeds he committed that permitted his being cursed. They may argue that he was a flagrant sinner and that every flagrant sinner may be cursed. Or they may hold that someone who commits a sin may be cursed even without being judged a flagrant sinner, just as the opposing sides at Siffīn cursed one another in the supplication during prayer. Thus, ‘Alī and his companions cursed particular men from Syria in their prayer supplications, and the Syrians likewise cursed their opponents. Yet when the combatants act on a defensible interpretation—both those in the right and those in rebellion—none of them is thereby deemed a flagrant sinner.
He may also be cursed specifically for his grave sins, even if other flagrant sinners are not cursed, just as the Messenger of Allah, may Allah bless him and grant him peace, cursed certain categories of sinners and particular individuals, without cursing them all. These, then, are (three grounds for cursing him.
As for those who considered loving him permissible, or who loved him, such as al-Ghazālī and al-Dastī, they have two grounds: