Cursing Ali (as) is tantamount to cursing Allah (swt)...
Cursing Ali (as) is tantamount to cursing Allah (swt) "Whoever curses (or verbally abuses) Ali, he has, in fact, cursed me, and whoever has cursed me, he has cursed Allah, and whoever has cursed Allah, then Allah will throw him into he Hell-fire." Musnad Ahmad Ibn Hanbal, v6, p33 Hanafi Fatwa declaring it kufr to curse Hadhrath 'Ali (as) In Sharh Mishkat Volume 11 page 345, esteemed Hanafi scholar Mulla Ali Qari states: 'Imam Ahmad narrates from the Prophet(s) "Whoever curses Ali, he has, in fact, cursed me, and whoever curses me, has cursed Allah.", this hadith means that cursing Hadhrath 'Ali is kufr'.
Fatwa of al Muhaddith Shah Abdul Aziz - those that curse 'Ali are kaafir In Tuhfa Ithna Ashariyya Shah Abdul Aziz states on page 394: "If the people of Syria i.e. Mu'awiya and his supporters bore enmity towards 'Ali(r), considered him a kaafir and cursed him, then I consider such people to be kaafir". As is habit of the Ulema of his like, Shah Sahib has sought to cast doubts as to whether Mu'awiya did indeed curse Maula 'Ali (as).
Fortunately as is common amongst such scholars his contradiction is exposed by the fact that he himself admitted in Fatwa Azeezi that Mu'awiya would curse Maula Ali (as). Similarly the Grand Imam of the Nasibis Ibn Taymeeya whilst tactically avoiding to implicate Mu'awiya make this admission is his Fatawa Volume 2 page 408: "The followers of Mu'awiya would curse Hadhrath 'Ali".
If those that curse Maula Ali are kaafir then from the Shah's own pen Mu'awiya IS a kaafir as are those that entertained this action. Fatwa of al Muhaddith Shah Abdul Aziz - whoever disrespects Ahl'ul bayt (as) is a murtad In Tuhfa Ithna Ashariyya Shah Abdul Aziz states on page 263: "What view should we hold of those people who express happiness on Ashura when Imam Hussain was killed, who marry on that day who disrespect the family of the Prophet and the descendents of Sayyida Fatima?
It is correct to refer to such individuals as Murtad". If one who shows disrespect towards Ahl'ul bayt (as) is a Murtad then clearly one of the rank and file of Mu'awiya who demonstrated his disrespect of 'Ali (as) by introducing the cursing of him in the Mosques comes at the fore-front of such murtads. Moreover one should also highlight Mu'awiya's pleasure upon receiving the news that Imam Hasan (as) was dead.