I would not comment on religious aspect of this issue, for its up to Allah, but speaking strictly from worldly political point, Amir Muawiya did rebel against the legitimate government of his time. However, i woud agree that he was an outstanding General and tactician, which he proved many times, during his wars in Syria and also in Siffin, where he had almost lost the battle but succeeded in inflicting severe blow to unity of Imam Ali's camp, which never recovered after this battle.
really a great comment ............ jazakullah