From their 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 Khawaarij al-Maariqoon (those who have gone outside the practice of the religion according to the way of the Prophet Muhammad ﷺ). This is due to them judging for themselves that they are the ones holding on to the Book of Allah and His Sunnah — and Alee, Mu'aawiyah, and the soldiers (who were with them) 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 Khawaarij up until today. And this is a great danger.
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 having the solutions to the problems of the Muslims, this is the beginning of the methodology of the Khawaarij. Indeed the true inheritors of the Prophet Muhammad ﷺ are the scholars of the Sunnah.