Are the Khawarij disbelievers?

Question:
May Allah reward you, Honorable Shaykh. This questioner says: Some scholars have declared the Khawarij to be disbelievers, citing the saying of the Prophet (peace and blessings be upon him), "I will kill them as 'Ad was killed." Others have not declared them disbelievers, citing the statement of 'Ali (may Allah be pleased with him) when he was asked, "Are they disbelievers?" He said, "No, they have fled from disbelief." So, which of their two positions is the stronger?

Answer:
Yes. The scholars have disagreed on declaring the Khawarij disbelievers. The majority hold that they are not disbelievers, but rather a group of rebels. The fact that 'Ali (may Allah be pleased with him) fought them, and that the Prophet (peace and blessings be upon him) ordered them to be fought, was not because of their disbelief. Whoever seeks to break the bond of obedience and seeks to make the blood of Muslims lawful must be fought, even if he is a Muslim. Therefore, the fact that they fight does not indicate their disbelief. Whoever attacks Muslims with the intent of breaking the bond of obedience or making their blood lawful must be fought, even if he is a Muslim. Yes.