Ahl as-Sunnah avoids takfir (accusing another Muslim of being an unbeliever).
In the history of Islam, there have always been groups and individuals committing takfir. They say that "the other group" has exited Islam acting upon their words and deeds and always preferring the aspect of their words and deeds that seem to be likely to exit Islam and refusing to interpret them in favor of that group.
There are scholars who deal with a word and deed taking into consideration all of the other words and deeds of a person holistically, who prefer "the possibility of that person's remaining a Muslim" and who accept him as a Muslim whenever possible. This attitude is the attitude of Ahl as-Sunnah, who say, “We do not accuse those whose qiblah is the Kaaba of unbelief.”
There are deviations from what is true regarding the rights and obligations of political opponents.
Let us deal with the issue taking the example of Hz. Ali into consideration:
Interpreting the verse “Allah is the best of judges” (al-An'am, 6/57) in accordance with their own interest, Kharijites, who were against Hz. Ali, the Caliph, regarded it as a cause of unbelief when Hz. Ali left the solution of the problem to judges related to the conflict with Muawiya and they addressed Hz. Ali as follows: “You have become an unbeliever.”
Sarakhsi, who is a great scholar of fiqh (Islam, worshipping and law) underlines two important rules while dealing with this issue:
1. Hz. Ali did not act in the same way against this severe accusation; he accepted them as "his brothers in religion" since they based their decree on the interpretation (though it was wrong) of a verse; he gave them the right to live and speak. Then, according to Ahl as-Sunnah, “there is no takfir if there is tawil (interpreation)”.
2.The rebels who harmed the property and lives of people acting upon the interpretation (though wrong) of a Quranic verse do not pay for the damages due to what they did when they regret and surrender.
Here is the statement of Sarakhsi:
“The evidence regarding the issue is the following narration reported by Zuhri:
"When mischief (revolt, chaos, conflict) occurred among Muslims, the believers (Companions) of the era of the Prophet (pbuh) were alive; they agreed on the following decree: any blood shed based on the interpretation of the Quran, any sexual intercourse based on the interpretation of the Quran and any destruction of goods based on the interpretation of the Quran are not subject to punishment and compensation even if those interpretations are wrong according to the other party who is right."
"The different interpretations of two Muslim groups who fight due to interpreting the religion differently are treated equally before law. It is a principle.”
Nowadays, the supporters of takfir (Iran, S. Araba, ISIS,…) have been on the rise again. They accuse the believers who interpret one or more verses of the Quran differently and who deduce different decrees from them of unbelief. They execute the opponents who are against the administration or the administrator though they do not resort to weapons.
I want to remind them that what they do is the way of Kahirijites and that Ahl as-Sunnah did not act like that.