But note that reciprocity is almost the opposite of loyalty. That kind of tribalism is dysfunctional in the modern world, because:

• You can't necessarily rely on reciprocity in those tribal relationships any more
• You can achieve reciprocity in non-tribal relationships

Rather than a static loyalty, it is more interesting to ask how people move into and out of your ingroup? What elicits our feelings of sympathy for some more than others? What kind of institutions encourage us to sympathise with other people and stand in their shoes? What triggers our moral imagination?

I'd tell a story of co-operative trade forcing us to stand in the shoes of other people, to figure out what they want as customers, thus not only allowing co-operation between people with divergent moral viewpoints, but itself giving rise to an ethic of conscientiousness, trustworthiness, and self-discipline. The "bourgeois virtues" out-competing the "warrior ethic."