God, the Exalted, Who is the source of mercy and blessing, has condemned and cursed many people in the Quran. They include people who hurt God and His messenger. The hypocrites and pagans, male or female, and those who conceal the clear signs of Allah, the Jews who believed that Allah's hand is tied up and those who accuse chaste and faithful women of evil acts have been cursed by God, the Glorified.[1]

All of these indicate that some people, given that they are free, commit so many evil acts that they make themselves entitled to divine punishment. The breeze of divine mercy, as per the teachings of the Quran, the Prophet (pbuh) and the Ahlul-Bait, will blow on those who put themselves in its direction. The Quran speaks of those who are doomed to eternal punishment in Hell.[2]

If an order (commandment) comes from God, or the Prophet and Imams (a.s.) to curse a certain group of people, we conclude that they are people who have closed all the ways of divine mercy to themselves; they are the ones who are submerged in sins and defiance of God to the extent that there is no hope left for their salvation. Although Imam Ali (a.s.) and Imam Hussein, as you have rightly mentioned, guided every individual to the truth, they would deal with them in the severest manner, if they did not accept it. Basically, why should not one speak of an oppressor and curse him on account of his evil deeds?

The case of people like Abu Lahab is still open even now after more than one thousand years. The Quran says: "Perdition overtake both hands of Abu Lahab, and he will perish!"[3]

Dissociating and detaching oneself from the enemies of God and the Ahlul-Bait (a.s.) is one of the basic commandments of the Shi'a religion. Loving the friends of Allah and the Ahlul-Bait (a.s) would be meaningful only when one detaches himself of their enemies. According to some traditions, cursing the enemies of God and Ahlul-Bait (a.s.) have been given preference over extending greetings to Ahlul-Bait (a.s.).[4]

Definitely, we do not hate the faithful people who sometimes commit an offense; rather, we detest their actions and deeds. What about the people who despite knowing the truth commit great sins like killing the prophets and imams?

It has been narrated from Imam Kazem (a.s.) that he said: "Detest the deeds of our friends who commit offense, and detest not them themselves."[5]

However, those who committed injustice to the Imams who had come to help people by guiding them to the right path and bringing them close to divine mercy and those who denied the Imams their rights and shed their blood depriving mankind of their guidance and blessing made themselves entitled to the everlasting curse and damnation of God, the prophets and Imams (a.s.). They are doomed to eternal punishment because of their crime to deprive mankind of the light of guidance.