In All My Sons, why does Chris call his father "Joe McGuts"?

Chris calls Keller "Joe McGuts" after hearing Keller describe his return to the neighborhood after being released from custody. 

Keller says that instead of parking directly in front of his own house, he parked down the street so that he would walk past all of his neighbors. In this way he faces the skepticism and the suspicion of the neighborhood head on. 

Instead of avoiding the stares of his neighbors and their implicit accusations, he invites those stares and endures them and, in this way, attempts to present himself as a person with nothing to hide.