It's plain that your children sinned against him— otherwise, why would God have punished them? Job 8:4 (MSG)
My brother likes to relate a story from childhood about he and my sister sitting on opposite ends of a room in the house. Without warning, my sister would start screaming, "Mom! Tim's hitting me!" In fact, he was just sitting there quietly on the other side of the room, but my mother would come running in anger. Without even considering that my sister, five years Tim's younger and the only daughter, would lie and make up such a tale, mom would punish my brother for beating up on his little sister. [Authors note: I can neither confirm nor deny the truth of this story]
I find it interesting, as I make my way through Job, that not one of Job's friends grapple with the fact that there might be something at work in Job's story besides God. We are quick to come running and blame God for every bad thing that happens, but what about evil? What about Satan? What about the tragic consequences that follow fallen man?
We are told from the beginning of the story that evil plays a part in Job's tragedy, but evil appears to be completely absent from the world-view of Job's friends. Like a mother blind to the fact that her young daughter might be telling a fib, Job's friends are blind to a major player in Job's story.