How did john of damascus defend the use of icons during the iconoclast controversy?

Always aware of my own unworthiness, I would have kept silent and merely confessed my shortcomings to God, but all things are good at the right time. I see the Church which God founded on the Apostles and Prophets with the cornerstone of Christ his Son, tossed on an angry sea, beaten by rushing waves, and shaken by the assaults of evil spirits. I see rips in the seamless robe of Christ which wicked men have tried to pull apart, and His body cut into pieces (i.e. the word of God and the ancient tradition of the Church). Because of this I have decided it is wrong to hold my tongue, remembering the warning in the Bible: “If you see the sword coming and do not warn your brother, I will hold you guilty of his blood.”