If refusal to give allegiance to an elected nominee was prohibited in Islam...

If refusal to give allegiance to an elected nominee was prohibited in Islam, Imam Ali would not have allowed himself to delay in giving his allegiance. In the same tradition in Sahih al-Bukhari, Imam Ali (AS) said that he had some rights in Caliphate which was not honored, and he complained why Abu Bakr should have not consulted him in deciding upon the ruler.

He later gave his allegiance when he found that the only way to save Islam is to leave the isolation which occured due to his refusal of giving the oath of allegiance. What's more? The well known companions, Abdullah Ibn Umar and Sa'd Ibn Abi Waqqas, refused to give their allegiance to Imam Ali for the entire duration of his caliphate. (Ibn Al-Athir, his history Al-Kamil, v3, p98). But the Imam did not punish these companions.

If it was permissible for a Muslim, who was a contemporary of the caliph, to refuse to give his allegiance, it would be more permissible for a person who came in a later century to believe or not to believe in the qualifications of that elected caliph. In doing so, he would not be sinning, provided that the Caliph is not assigned by Allah. The Shia say that Imam must be appointed by God; that appointment may be known through the declaration of the Prophet or the preceding Imam.

The Sunni scholars say that Imam (or Caliph, as they prefer to say) can be either elected, or nominated by the preceding Caliph, or selected by a committee, or may attempt to gain the power through a military coup (as was in the case of Muawiyah). The Shi'a scholars say that a divinely appointed Imam is sinless and Allah does not grant such position to the sinful. The Sunni scholars (including Mu'tazilites) say that Imam can be sinful as he is appointed by other than Allah.

Even if he is tyrant and sunk in sins (like in the case of Muawiyah and Yazid), the majority of the scholars from the schools of Hanbali, Shafi'i, and Maliki discourage people to rise against that Caliph. They think that they should be preserved although they disagree with the evil actions. The Shia say that Imam must possess above all such qualities as knowledge, bravery, justice, wisdom, piety, love of God etc. The Sunni scholars say it is not necessary.

A person inferior in these qualities may be elected in preference to a person having all these qualities of superior degree. Previous…