Shaikh Saaleh al-Fawzaan [may Allaah preserve him] said:
The khawaarij were not misguided and misguiding others with their intellects and fear of Allaah, except that they disassociated themselves from the scholars and depended on their own understanding and that of those similar to them. They took instructions from one another, and thus they caused harm to themselves and to the Ummah. This is the result of disassociating from the scholars.
Source: Tawjeehaat Muhimmah Li-Shabaab al-Ummah