The passion of anger, in which one may include all forms of aggression toward other people, is also bears evidence of the absence of love for one’s neighbor. Meekness, gentleness, (a virtue that is the opposite of anger) is an expression of love; some of the Holy Fathers even equate meekness with love for one’s neighbor.

Archimandrite Sergius (Shevitch)

The Lord does not accept prayers offered in anger… Where there is no peace [among people], there is the enemy and darkness, and spiritual weariness, and the rest of elements of hell.

Abbot Nikon (Vorobiev)