Why were the Hesychasts accused of iconoclasm?
The Hesychasts were accused of iconoclasm, because they believed that images should not be used or accepted in prayer. This was misunderstood by the anti-Hesychasts as a rejection of Orthodox iconography, and so they likened the Hesychasts to the Messalians (Bogomils), because the Messalians, among other things, rejected all images, including icons, and claimed to be able to experience the vision of the essence of God through their natural, physical senses. But what the Hesychasts rejected was, in fact, not iconography per se but the naturalistic portrayal of Christ and the Saints in religious paintings, regarding the naturalistic style of iconography as a “window” into this world instead of the World-to-Come. It was the duty of the Church, as the Hesychasts saw it, to point to God’s purpose in His creation of man - to the transfigured and deified human person in Christ. What the Hesychasts sought after in their own style of iconography was thus the representation of sanctified or glorified or deified human beings - the “final glory” of man in the kingdom of Heaven.
What the Hesychasts were referring to, moreover, in their rejection of images during prayer, was the discernment of thoughts (logismoi, Gk. λογισμοί), which were often ῾image-bearing῾, that is to say, ῾tempting thoughts῾ accompanied by images produced by either the human mind or the enemy (demonic powers). Being a product of human or demonic fantasy (Gk. φαντασία), the novice would be advised to reject all images, until reaching a certain spiritual maturity, by which time he or she would be able to “discern the spirits”; recognizing in other words which thoughts come from God, which from the enemy, and which are the product of man’s own spiritual world. Needless to say, it is very important to accept thoughts which come from God, and to reject those that come from the enemy, and even those which are of the human mind. This discernment, however, is acquired over time, and results from learning the humble way of Christ through the practice of obedience to the will of God.