I’ve been looking through John Krumm’s Modern Heresies again. Published in 1961 and out of print now, second-hand copies can be obtained inexpensively here.
From the chapter “Is Original Sin a ‘Moral Hypochondria’?”:
The doctrine of original sin does not all by itself determine man’s decisions, but it does set them in a context of modesty and compassion and tolerance. It checks man’s perennial temptation to cast all his judgments in the form of black or white, absolutely good or absolutely evil. It opens a man’s ears and eyes to what others say and enables him to sympathize with them more fully….Self-confessed sinners meet one another in an atmosphere of mutual suspicion but of mutual sympathy and understanding as well. “He is a sinner—but then, so am I.” So the doctrine of human sin draws out of human conflicts and controversies the sting of ferocity and vindictiveness. By locating the center of the human problem in the self-assertiveness and imperialism of the human heart, the doctrine of original sin makes a man modest about all human programs—even his own—and sensitizes his conscience to the lingering elements of willfulness and prejudice in his best judgments and most altruistic actions. (my emphasis from the first time I read it).