This book offers an answer, but is a work of opinion, not scholarship - in part because making sure everyone understands that this is entirely a work of opinion may deflect some lawsuits; in part because making it a collection of stand-alone essays allowed me to use some older stuff; but mainly because I do not want to hide a bunch of blunt assertions behind the usual academic camouflage - gently reinterpreted quotations from our elders.
A National Review article from a few years ago by one M.D. Aeschliman shows why by illustrating both the scholarly process and its weaknesses: it's beautifully written, full of scholarly references, and clearly intended to make a cogent argument for something - but what exactly that something is, I do not know - and I've read it twice.
Consider this bit, chosen because it can be read to support one of the key arguments in this book - that Christianity, Socialism, and the American revolution all reflect the same core values:
Moyn's book eschews any triumphant progressive narrative about human rights of the kind that looks to the ancient Hebrews, the Stoics, the Christian Church, or the 18th-century French "Enlightenment" for an initial agenda that "in the fullness of time," over decades or centuries, is finally worked out in a coherent, secular ethical consensus and body of international law. He knows that 20th-century history was both apocalyptic and tragic and that there is no guarantee that 21st-century history will be better. The "Thousand-Year Reich" lasted twelve; Bolshevik "scientific socialism" produced not utopia but massive amounts of death, destruction, and demoralization; commercial capitalism produces increasing cultural degradation and gross inequality; Islam is at best morally ambiguous; China is no exemplary moral picture; Venus has not triumphed conclusively over Mars.
Yet Moyn's book is invigorating in showing that the beliefs and actions of certain traditions and individuals have borne fruit in the intermittent diminution of human suffering and injustice and the intermittent increase in human decency. Almost in spite of himself, he ends up showing the profound, prominent, and prophetic role of the early 20th-century Catholic Church in promoting the universal idea for which Locke and Lincoln stood and that Habermas noted - the idea that the belief that every human being is "made in the image of God" means that each human being ought to be treated as an end, not merely a means; a subject, not merely an object; an essence, not merely an existent; a person, not merely a thing. Though human rights are historically rooted in monotheistic religion and Graeco-Roman Stoicism, and were given an unstable secular basis by Kant, Moyn shows that it was in Christian doctrines, developments, institutions, and individuals that they reached mature and consistent articulation.
I have no idea how the editors at National Review saw this article, but I see it as a kind of cri de coeur from someone who clearly has read a lot of stuff and probably understood more of it than I did, but who simply can't bring himself to articulate the obvious: that socialist thought is Christian thought, but socialist action is the opposite - and therefore that the people who define themselves by their Christian, humanist values but rail against Christianity while acting against their own humanist values at every opportunity must be doing so under some unknown, but terrible, compulsion.
What I think he wants, and by assumption what I think most people looking at the record probably want, is to see people involved in traditional socialist activities like electoral fraud, mass murder, racism, and the violent suppression of dissent as basically good and decent people who can be saved by removing the gun pointed at their heads - but this is, of course, delusional because there is no gun, no obvious external force. Most people want desperately to believe, for example, that sixty million decent Germans went along with killing their neighbors because they were afraid of Hitler's brown shirts, SS, and other enforcers; but the truth is that millions were proud to wear those brown shirts and jackboots - and that could not have happened without the emotional support of many millions more among family and friends.
There is an academic case to be made for the underlying explanation: that both the fascist reversion to feudalism and the cultist's violent reaction to disproof have deep roots in the pre-human psyche; but this book isn't the place for it. This book is intended as a sledgehammer breaking open the door to further discussion, causing good progressives everywhere to turn away in an agony of righteous disgust, while making a small start on allowing kids everywhere to wear their MAGA caps to schools and universities without fear of retribution by teachers and others.