Opposing one another is slavery to the Enemy
“The Saviour has taught men what they could never learn among the idols. It is also no small exposure of the weakness and nothingness of demons and idols, for it was because they knew their own weakness that the demons were always setting men to fight each other, fearing lest, if they ceased from mutual strife, they would turn to attack the demons themselves. For in truth the disciples of Christ, instead of fighting each other, stand arrayed against demons by their habits and virtuous actions, and chase them away and mock at their captain the devil. Even in youth they are chaste, they endure in times of testing and persevere in toils. When they are insulted, they are patient, when robbed they make light of it, and, marvellous to relate, they make light even of death itself, and become martyrs of Christ.” – St Athanasius the Great, On the Incarnation, Chapter 8, 52