Something rather insightful from Fr Gabriel's book called "Dragon's Wine and Angel's Bread."
Pages 72-74, SVSP [St. Vladimir's Seminar Press], 2009
Father Bunge: The demons, then, are opposed not only to the virutes in that they tempt us to their contrary vices but also in the domain of theology to the dogmatic teachings of the Catholic and Apostolic Church.
Monk Evagrius: In this way wherein I have walked they hid for me a snare: Our enemies lay a trap in all the virtues. In courage they conceal the snares of cowardice; in prudence, those of fornication; in love they lay the snares of hatred. Into meekness, they instill arrogance; into compassion, a mercifulness not for God's sake but for the sake of the onlooker...And indeed what must one still say about contemplation and how many snares the ehemies have laid through heresies against Orthodox teaching.
Father Bunge: Heresies are therefore not mere dogmatic errors, comparable to scientific errors, but rather the work of demons in the heads of those who hatch them or fall to them. Evagrius assures us that he has even experienced this in his own life.
Only those whose spirit has been previously blinded by the demon of anger and who have incurred the loss of the divine light of knowledge are susceptible to such demonic blindings...As we have seen above, the demonic thought blinds the soul's left eye, which is devoted to the contemplation of the created...Evagrius' notion is still thought provoking: That moral defects, without fail, have consequences in the domain of knowledge and spiritual contemplation; and conversely that every kind of heresy is not simply an intellectual failure, but a work of the demons in the ones they have previously blinded through the vice of anger.
How different church history would look, had all those involved in dogmatic disputes taken greater care to beware the signs of anger. And not only then, when with supposedly holy zeal, they took to the field against alleged or actual false teachings but also in all those conflicts that have led to divisions within the Church. Evagrius is convinced that the schisms of Church history as well are nothing else than the work of demons, and above all the demon of anger.