48:18 The Baya under the tree, Ammar (ra), the one who killed him and the hadith of the Holy Prophet (PBUH&HF)?

Imam Ali AS was on Haqq(truth), in all of the fitna wars that were waged against him....if cursing Mauwiyah makes one a kaffir, than what the hell does it make Mauwiyah for killing Ammar RA, Hujr RA and son of Abu Bakr, Muhammad and killing other Sahabah? What does that make Mauwiyah for cursing Imam Ali AS?? What is the status of Yazid for attacking the people of Medina and killing the last generation of the remaining Sahabah? How is it these guys are praised and called Muslims yet cursing them makes one a kaffir?