Culture can be defined as the total knowledge, experience, beliefs, values, and attitudes, of a group of people. Probably the best example of culture that I can think of in "The Outcasts of Poker Flat" is the cultural attitude expressed by the people of Poker Flat.  The story begins with John Oakhurst, Duchess, Mother Shipton, and Uncle Billy being thrown out of town.  Oakhurst is a gambler.  Duchess and Mother Shipton are prostitutes, and Uncle Billy is a violent drunk.  It's a testament to Poker Flat that they are not willing to have those kinds of morally corrupt people in their town.  Their beliefs and values system doesn't allow tolerance of degenerates in their town.  You could make a claim that their culture is a non-tolerant culture, but that still would describe the culture that the town of Poker Flat is trying to establish.