Haidt speculates on how such a split could have arisen:
How did it come to pass that in much of Europe, and in some parts of the United States, moral concerns have been restricted to issues related to harm/welfare/care and justice/rights/fairness? We believe that a team of historians and sociologists could easily tell such a story, probably involving references to the growth of free markets, social mobility, science, material wealth, and ethnic and religious diversity. Mobility and diversity make a morality based on shared valuation of traditions and institutions quite difficult (Whose traditions? Which institutions?). These factors help explain the electoral map of the United States in the 2004 presidential election. When viewed at the county level, the great majority of counties that voted for John Kerry are near major waterways, where ports and cities are usually located and where mobility and diversity are greatest. Areas with less mobility and less diversity generally have the more traditional five-foundation morality, and therefore were more likely to vote for George W. Bush – and to tell pollsters that their reason was “moral values.”
Of course, historians and political scientists have long told this tale. Liberalism has long been held to be a "least common denominator" morality which truncates traditionalist ethics for the sake of peace in the wake of destroyed religious unity. Many also note how reductionist ethics increase business opportunities by opening up markets for what was once regarded as sacred, or redirecting loyalty towards brands instead of towards people. As standards become increasingly utilitarian this reductive spirit sidelines other considerations, hampering one's ethical growth.
The wider vocabulary of traditionalist ethics allows for greater nuance in theory. Though friendship or marriage, for instance, can be understood as matters of harm and care or fairness and reciprocity, the concepts of loyalty and purity provide further layers for ethical exploration and discussion. Likewise the abandonment of such categories renders the critic powerless to correct their abuses. The lazy secularist must dismiss all appeals to holiness, while a writer genuinely concerned about the sacred is better equipped and motivated to eviscerate cant masquerading as piety.