While perusing the “Anti-Civilization” section of Left Bank Books in Seattle recently, I came across a nonfiction book on how to survive zombie attacks. The author instructed readers that while churches are generally to be avoided, church buildings, with their thick walls and heavy doors, can provide protection from the “living dead.” As Mary Eberstadt shows in her new book, Christian churches are actually under attack from the living Left, which is engaging in a massive assault on religion — and the church walls might not prove as strong as they look.

Eberstadt’s catalogue of actions by these groups to suppress religious liberty will startle readers, even those who have followed the stories of fines against bakeries for their refusal to provide services to gay weddings, the attempt to force the Little Sisters of the Poor to provide contraceptives in medical insurance, Brendan Eich’s ouster as CEO of Mozilla because he contributed to a proposition campaign in California affirming traditional marriage, and the Houston city council’s issuing of subpoenas ordering pastors to turn over sermons mentioning homosexuality or gender identity.

All these cases gained national attention, but Eberstadt shows that the national media have ignored dozens of other assaults on religious liberty. InterVarsity and other Christian student groups have been thrown off campuses across the country because they refused to sign university “non-discriminatory” clauses in support of same-sex marriage. In Atlanta, an Evangelical Christian fire chief was suspended for writing and self-publishing a book professing his Christian beliefs; Catholic and other Christian adoption and social-service agencies are under legal siege because of their support for traditional Judeo-Christian marriage; military chaplains and personnel have been punished for wearing pro-life buttons or displaying personal religious symbols on their desks; and public-school teachers have been fired for explaining Biblical passages to their students. These attacks are so numerous that they are cause for genuine alarm.

There has been a well-organized campaign against Christianity, making use of new interpretations of the concepts of free speech, civil rights, and social justice. Eberstadt argues correctly that this assault goes to the very core of our founding constitutional principles of freedom of worship and free association, embodied in the First Amendment. The Founders understood that political liberty and religious liberty were fundamental to a well-ordered republic. It was not coincidental that it was the very first amendment in the Bill of Rights that ensured the protection of the free exercise of religion. Legal scholar Philip Hamburger showed in his magnificent study Separation of Church and State (2002) that the Jeffersonian-Madisonian concept of erecting a high wall separating church and state was rejected by Congress when it enacted the First Amendment and did not gain traction in legal discourse until anti-Catholic campaigns in the late 19th century. But Congress did enact the free-exercise clause, and meant it.

The concept of religious toleration came slowly to the West and to America. Some scholars point to evidence of ancient Romans’ tolerating other religions in their empire and Muslims’ toleration of Jews in their empire, but these cases are misleading. Romans tolerated religious cults provided they did not threaten state religion, and the Muslim concept of toleration allowed Jews to practice their faith, provided they paid a tax to local caliphates. These policies did not incorporate the ideas of free association and free speech embodied in the Western concept of religious toleration.

Eberstadt finds the concept of religious toleration in the West in the 18th-century European Enlightenment. She could have looked farther back in European history: The beginnings of the modern concept of religious toleration are found in the Treaty of Westphalia, which followed the Thirty Years’ War (1618–48), and the Glorious Revolution in England in 1688. The Thirty Years’ War, which began as a religious struggle between Catholic and Protestant principalities, degenerated into a barbarism that left entire villages devastated and destroyed economic, cultural, and moral standards. The terms of the Peace of Westphalia ending the war allowed for the recognition of the primacy of Roman Catholics, Lutherans, and Reformed Protestants within their own principalities. Religious minorities in these jurisdictions were subjected to various kinds of pressure and occasional persecution, but the first seeds of religious toleration had been sown.

A more important step toward religious toleration came in England with the Settlement of 1688, which replaced the Stuart dynasty with William of Orange. Under William, the Church of England allowed the modest integration of nonconformist Protestants into the church. In this context, English philosopher John Locke, the great apologist for the Glorious Revolution, wrote his “Letter Concerning Toleration” in 1689, arguing for toleration of Protestant religious groups. Roman Catholics continued to be excluded from holding public office, but local officials began to turn a blind eye to restrictive laws against Catholics.

The greatest advance toward religious liberty and religious toleration came in America with the drafting of the U.S. Constitution. The myriad Protestant denominations and sects created a pluralist environment that made it impossible for one group to dominate the religious order. Yet even in this environment, religious toleration was not complete. Many states continued to bar Roman Catholics, Jews, and Muslims from holding public office. These discriminatory laws and local ordinances quickly broke down, however, owing to republican culture and mass immigration.

The illiberal assault on religious liberty today represents a return to the past in which people were persecuted for their beliefs. Unlike the persecutions of the past, in which people were burned at the stake, today’s persecution of Christians takes place in the courts, the administrative bureaucracies, and the forum of public opinion. At issue, as Eberstadt correctly observes, is “nothing less than the future of free speech and free association.” On the surface, the intensity of the persecutor’s mind is difficult to explain. Why are those acting in the name of “diversity” and “tolerance” so intent on uniformity of thought and culture? Eberstadt says the “quasi-religious” belief of these reactionaries is invested in the sexual revolution: “It is that sex between (and among) consenting adults is good — and since sex is good, the more sex, at least in theory, the better.” The sexual revolution, which began in the 1960s, is “not libertarian.” It is instead “neo-puritanical — that is, it is aimed at safeguarding its own body of revealed and developed truths, and at marginalizing its traditional competition.”

She observes that this “religion of sex” mimics traditional religion with its own “hagiography of secular saints, . . . proselytizers for abortion and contraception, like Margaret Sanger and Helen Gurley Brown and Gloria Steinem; crypto-scholastics whose work is revered by generation after generation of the faithful and off limits for intellectual revisionism.” These saints are joined by a “full-blown secularist martyrology, according to which tragic deaths like those of Matthew Shepard or Harvey Milk achieve supercommunal status and symbolism.”

Eberstadt’s understanding of the quasi-religious nature of this anti-Christian crusade is poignant. Theologically, the tone of the sexual revolution devolves into a kind of pre-Christian gnosticism, in which believers have a secret knowledge unknown to the masses. Unlike the gnostics of the past, who were sexual ascetics obsessed with the spiritual universe, the mystery cultists of the sexual revolution are obsessed with the carnal world. The modern-day gnostics project themselves as an enlightened class willing to overturn centuries of faith and practice about sexual relations and the importance of family in maintaining a well-ordered society.

In their own eyes, they hold a revealed knowledge that sexual identity and the family are social constructions created by a patriarchal, oppressive society. Eberstadt understands that the foundation of the secular/progressive worldview is the doctrine that “the Pill and its backup plan, abortion on demand, have liberated humanity — first, by freeing women from the chains of their fertility, and second, by having broken down the door to the fortress of traditional morality, after which one sexual minority after another has been liberated.”

Eberstadt compares the anti-Christian onslaught today to the witch hunts in 17th-century New England and the anti-Communist hysteria in the 1950s. These analogies are somewhat misleading. New England Puritan leaders prided themselves on being rationalistic and scientific-minded. However misplaced their concerns about actual witches, they sought empirical evidence of the devil’s hand at work in the natural world. In the end, they concluded — too late for many who were sentenced to death as witches — that scientific proof was lacking for further trials. Today’s anti-Christian witch hunters, who look for signs of sexism, homophobia, and cisgender prejudice, are driven not by reason or historical experience, but by sentiment and passion. No facts to the contrary will dissuade them from their effort.

And whatever the ills of McCarthyism and its false accusations, there were actual Communists at work in America in the 1950s. We know from the Soviet archives and U.S. intelligence sources that there were over 300 American spies working under the directives of Moscow. Contrary to the anti-Christian propagandists of today, American culture is not permeated by widespread prejudice against women and homosexuals.

The movement against Christians and organized religion today has hysterical overtones, but it is a well-calculated endeavor. It is led by activist lawyers, foundation officers, government bureaucrats, and college-educated secularists. Secular non-believers are becoming a majority in Europe and America, especially among the youth. If Christians become the minority in America, this is all the more reason to protect their fundamental rights of free speech and free association against the “tyranny of the majority.”

Eberstadt remains optimistic that in this war on Christianity, as in previous moments of hysteria, common sense will ultimately prevail. A religious awakening, such as those that occurred in the 1740s and in the 1830s, can reverse the decline in American culture. Meanwhile, the task of Christians is to continue to defend their rights, evangelize for their faith, and involve themselves in their communities to produce good works.

Eberstadt concludes: “Courage is required for people like that to stand not only against the cultural tide, but against the inner worms of human nature.” Christianity was founded on the persecution of its Savior and a belief that faith and reason will ultimately prevail.

The “Anti-Civilization” section of Left Bank Books in Seattle has replaced the “Marxism” section, which is now just a small shelf of dusty books. Faith in progress and reason is being sorely tested these days.

– Mr. Critchlow, a professor of history at Arizona State University, is the author of Future Right: The Forging of a New Republican Majority.