In chapter 6, which is also part of the novel, Gladwell begins with a description of Harlan, and how this little known rural town was popularized by two immigrant founding families. He sets this description up to make it clear that this unassuming place, with all of its simplicity and beauty, was still rocked by the actions- and culture- of how people were raised, and how they were born.
Gladwell goes on to say that individual families fighting each other is a feud, but multiple families fighting in this way is a pattern (See page 166). This pattern has been most notably explained as a culture of honor.
In essence, a big takeaway is that people are products of not only how they are raised, meaning their environments, but also how they are raised. To see evidence of this, Gladwell explains that the region along the Appalachian Mountains, which includes Harlan and many of the scenes for the most violent and notable family feud, is due in part because of the people who settled that area. Those individuals were of Scottish-Irish decent, and they fully believed in honor and a code of such in their lives. For them, this culture of honor is as intrinsic in their lives as the blood that courses through their veins.
Gladwell further explains this code of honor by illuminating the Southern region of America. He explains that the South is more violent than others places, due to this same culture of honor. He states,
Cultural legacies are powerful forces. They have deep roots and long lives. They persist, generation after generation, virtually intact, even as the economic and social and demographic conditions that spawned them have vanished, and they play such a role in directing attitudes and behavior that we cannot make sense of our world without them (See page 173 of Outliers).