Eliphaz felt the force of what Job said (and for this reason probably avoided interacting with it in detail), but he saw it as highly dangerous talk. He saw it as destructive to Job and corrupting to anyone else taken in by it.
How could Eliphaz so misjudge Job as to see him as a man driven only by iniquity? Was he to blame for this wrong assessment? Certainly, and God later rebukes severely him for it. This attack on Job was a defence of himself and his own false theology. A man cannot hold a position as much at odds with the truth as Eliphaz did and not be to blame. His system of theology was ostensibly designed to vindicate the righteousness and honour of the Lord, but in reality it took away from God his perfect standards. It made the Lord to be one who was content to accept human beings in their own righteousness, rather than insisting on accepting them only when clothed with the righteousness of God. It was a subtle attack which left Job struggling to disentangle himself from its snares. Job was a sinner in Eliphaz’ eyes, because, in his attempts to understand the ways of the Lord, he questioned how God could treat one who trusts him with such harshness and without any apparent cause. (Later he was to discover that there was a very important cause.) He therefore frets greatly in his confusion and his faith is unable for the moment to surmount this obstacle. Eliphaz has a much simpler view of the world, but it is a view that is only possible if God’s perfections are taken from him: God rewards men strictly according to their behaviour and therefore, if Job is punished while Eliphaz is not, it is because one is a hypocrite and the other is pleasing to God. He was wrong on both accounts.