All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
‘Urs ibn ‘Umayrah Al-Kindi narrated that the Prophet said: “If a sin is committed on earth, the one who witnessed it and hated it [i.e. was not pleased with it] is like the one who was absent from it, and the one who was absent from it but he was pleased with it, is like the one who witnessed it [and was pleased with it].” [Abu Daawood and At-Tabaraani]
This proves that if someone is pleased with evil, he is sinful even if he is absent from it. Therefore, whoever is pleased with the killing of Al-Husain he is sinful regardless of the era in which he lived. Indeed, how would a man who believes in Allaah The Almighty and in the Hereafter be pleased with this? In the past, Ibn Taymiyyah said, “As regards the one who killed Al-Husain or helped in his killing or was pleased with that, then upon him will be the Curse of Allaah and of the angels and of all the people, and Allaah will not accept from him either obligatory acts or supererogatory acts.” For more benefit on the stand of Ahlus-Sunnah on the killing of Al-Husain refer to Fatwas 87406 and 85186.
Allaah Knows best.