What is the nature of the conflict Marshal Potter feels on the train in Part1? Why does he feel that he committed a "crime" in bringing home a bride to Yellow Sky?

Potter's bride is of a lower class than Jack, and this is obvious to all they come across. Despite this, Jack, albeit worried about how they will be received, is happy to marry her and bring her back to his hometown. The conflict can be found in the way he hides his marriage bacause of the difference in their social standing.