The original question had to be edited down.  The townspeople are the reminder that American democracy is only able to function when there is a sense of open- mindedness.  The setting in which Drummond enters is one in which he is seen as Satan and Bert Cates is guilty without as much as a secondary thought.  Yet, over time, the townspeople are compelled to debate and to think about the arguments that Drummond presents.  

This ability to think is where the townspeople provide the ultimate validation for the trial.  The townspeople's ability to think and to weigh for themselves the validity fo the arguments presented demonstrates the importance of being open- minded.  The townspeople might have started the trial in one frame of reference.  As the trial has continued, they show themselves being open to what is being presented.  Like the story of Golden Dancer, the open- minded nature of the townspeople as the trial continues is one in which the reader is reminded that the sensibilities of a great democracy only work when individuals are able to think and evaluate in the recognition of truth. This is demonstrated in the open minded nature of the townspeople.