As long as we treat sin as a minor category, we will always question the atoning death of the God-man to solve our problem. Show me a person who questions the incarnation and you have shown me a person who takes the categories of sin and God's holiness rather lightly…..The second step is to belittle God. The biblical picture of God banishing Adam and Eve from Eden for eating a piece of forbidden fruit is replaced with a God who will basically put up with anything. He is a God more interested in sincerity than holiness, content to tolerate anything we do because he has a love affair with human free will.
….Once we have neutered God of the attribute of his holy wrath and toned down talk of sin by minimizing its dastardly effects - fashioning ourselves as good people who occasionally err - we have effectively removed the requirement for atonement. It is then a short step to questioning the incarnation. Why insist on God becoming human and solving a problem we are quite capable of solving ourselves? The modern propensity to downplay the divinity of Jesus is tied to a watered-down version of what constitutes sin, and a wishy-washy portrayal of a God too tolerant and friendly to worry about it.
Quote from his book:
The Language of Salvation: Discovering the Riches of What it Means to Be Saved