Shaykh Sulayman ar-Ruhayli writes:

From their [i.e: those upon khāriji ideologies like ISIS, Al-Qā’idah, etc] danger is their praise of themselves and their speaking ill of those who are better than them. Shaykhul Islam Ibn Taymiyyah (رحمه الله) stated: “The first to go astray in that are the Khawārij al-Māriqoon (Those who have gone outside the practice of the religion according to the way of the Prophet Muhammad صلى الله عليه وسلم). This is due to them judging for themselves that they are the ones holding on to the Book of Allah and His Sunnah and that Alī, Mu’āwiyah and the soldiers (who were with these two) are the people of disobedience and innovation. Therefore, as a result of that, they made lawful that which they made lawful from the Muslims.” This is the way of the Khawārij up until today. And this is a great danger.

Source: 92الأصول السنية البهية في كشف شبهة أهل الفتن الغوية ص

Translator’s Note: When you see individuals belittling the Scholars of the Sunnah, describing them with negative descriptions and at the same time praising themselves and presenting themselves as being the ones who are truly holding on to the Deen and they have the solutions for the problems of the Muslims, this is the beginning of the Methodology of the Khawārij. Indeed the true inheritors of the Prophet Muhammad صلى الله عليه وسلم are the Scholars of the Sunnah.

Translated by Abu Yusuf Khaleefah
6th of Muharram, 1439 (09-26-2017)
Masjid Nur Allah, Queens, NYC