What revelation does Gene have after Finny apologizes for the "feeling [he] had"? What does Gene attempt to do at that point?

After Finny tells Gene that he had a notion that Gene might have caused the fall but dismissed it and apologizes, Gene comes to the realization that if the guilty shoe were on the other foot........ Finny would have told him the truth. Gene attempts to tell the truth, but Finny shuts him down. He simply doesn't want to hear it.