I believe Sowell's argument is based on culture.
I don't see how one could deny cultures tend to inform folks of norms of behavior, especially when conflict arises.
I've never thought of it as a secret as to how Scots-Irish culture preciptated the region, especially in terms of conflict. The Hatfield and McCoys aren't just a family, but a stereotype of how conflicts arise and are handled. Even research shows a higher rate of violence in the southeast when it comes to 2 individuals that know each other and have a conflict.
Has nothing to do with intelligence, as Sowell points out. Same as for other groups that he points out. It is about culture in his opinion. I don't see anything wrong with critiquing our culture, especially as an Appalachian Scots-Irish. I think it could be better, as a whole. Even America in general. Too much about popularity, and yes even sports, not enough about praising everyday careers like doctors, engineers, accountants, teachers, computer programmers, IT, etc. Basically pushing education as a higher thing to reach for rather than praying and pouring in tons of resources to other things. That's jmo but there are a few cultures, even within America, that are superior in some ways. I'm not afraid to say it. We could do better.