From the chapter entitled "Our Attitude to the Sins of Others", here is just a small sampling of what Fr. John has to say:
You are angry with your neighbour, and say of him that he has done this or that, and so on. What business of yours is it? He sins against God, not against you. God is his judge, not you, and to God he shall give an account, not to you. Know how sinful you are yourself, how difficult it is for you to master your own sins, and to get the better of them, how afflicted you are by them, how they have ensnared you, how you wish indulgence from others. Your brother is a man like unto you; therefore you must be indulgent to him, as to a sinful man similar in all things to you, as infirm as you. Love him, then, as yourself: These things I command you, that ye love one another.
He who does any evil, who gratifies any passion, is punished enough by the evil he has committed, by the vice he has served, and above all by the fact that he withdraws himself from God, and God withdraws himself from him - it would therefore be insane, and inhuman, to nourish anger against such a man; one might as well drown a man who is already sinking, or push into the fire one who is already burning. To such a man, as to one in danger of perishing, we must show more love than ever, and pray fervently for him, not judging him, nor rejoicing at his misfortune.
Do not be irritated with those who sin; do not develop a habit of noticing every sin in others, and judging them, as we are so inclined to do. Everyone shall give an answer to God for himself. Correct your own sins; and amend your own heart.
This book can be purchased here at St. Vladimir's Seminary Press.