In 1934, the year after Adolf Hitler assumed power, the American Civil Liberties Union published a pamphlet entitled Shall We Defend Free Speech for Nazis in America? The answer was an emphatic yes. If the A.C.L.U. appeased critics who “condoned the denial of rights to Nazi propagandists,” the group asked, “in what position would it be to champion the rights of others?”

This is a good question as the A.C.L.U. celebrates its centenary. For it has become increasingly clear that the organization’s once stalwart commitment to the defense of free speech has gone wobbly.

In January, Simon & Schuster in conjunction with the A.C.L.U. releases Fight of the Century, a collection of essays by well-known writers commemorating its landmark cases. Among the roughly three dozen pieces are ruminations by Dave Eggers on Escobedo v. Illinois (wherein the Supreme Court granted criminal suspects the right to legal counsel while under police interrogation), George Saunders on Immigration and Naturalization Services v. St. Cyr (which reaffirmed the right of habeas corpus for immigrants who have committed crimes), and Aleksander Hemon on Loving v. Virginia (which struck down miscegenation laws). Conspicuously absent from this list, however, is the paradigmatic American free-speech case, one in which the A.C.L.U. played a highly controversial yet praiseworthy role: National Socialist Party of America v. Village of Skokie.

In that 1977 lawsuit, the A.C.L.U. defended a group of Nazis planning to march not just in any town, but one with a high concentration of Holocaust survivors. At the helm of the A.C.L.U. was Aryeh Neier, a refugee from Nazi Germany. Neier, now 82, is a man with sterling left-wing credentials who understands more than most the evil of extreme right-wing ideologies. And yet he believed then, and still believes now, that the constitutional rights of Nazis must take precedence over the sensitivities of those they might offend. “Keeping a few Nazis off the streets of Skokie will serve Jews poorly if it means that the freedoms to speak, publish, or assemble any place in the United States are thereby weakened,” he wrote in his memoir of the case, Defending My Enemy. “Defending my enemy is the only way to protect a free society against the enemies of freedom.”

George Lincoln Rockwell, head of the American Nazi Party, in 1960. That year, the A.C.L.U. sued the New York City parks commissioner, an N.Y.C.L.U. member, to defend Rockwell’s right to hold a rally in Union Square.

Neier’s reasoning left many A.C.L.U. supporters unconvinced, if not infuriated. The organization, which had increased its membership and budget massively in the preceding years thanks to Watergate and revelations of grave F.B.I. and C.I.A. abuses, lost half a million dollars in membership income as a result of its principled stand in Skokie—but it earned the admiration of Americans who cherish the First Amendment.

Conspicuously absent is the paradigmatic American free-speech case: National Socialist Party of America v. Village of Skokie.

Fight of the Century does contain essays defending “freedom for the thought that we hate,” Supreme Court Justice Oliver Wendell Holmes’s pithy summation of what a genuine commitment to the First Amendment entails. There’s an essay on Terminiello v. City of Chicago, which held that a “breach of peace” ordinance banning an address by a racist and anti-Semitic priest was unconstitutional, and another honoring Brandenburg v. Ohio, where the A.C.L.U.’s siding with a Ku Klux Klan leader led the Supreme Court to conceive the “imminent lawless action” test for determining whether certain speech could be considered illegal incitement. Indeed, there are even a few approving references to Skokie sprinkled throughout the book. Scott Turow writes that his own “moment of adherence” to the A.C.L.U. came as a result of its taking that case, a point he makes in an essay blasting the organization for opposing limits on political-campaign spending (which A.C.L.U. national legal director David Cole, in the foreword, holds up as evidence of the organization’s openness to dissent).

“The ACLU put together a long list of all their cases and the contributors got to choose which ones they wanted to write about,” the book’s publisher said in a statement via e-mail, when asked about the lack of an essay on Skokie. “The book is thus not comprehensive in this way, or supposed to be comprehensive.” But Skokie is arguably the most famous case in the A.C.L.U.’s 100-year history, and certainly the most controversial. Its glaring omission from a collection like this can only be seen as a craven attempt to erase a vital part of that history. It brings to mind Robert Frost’s observation that a liberal is someone so open-minded he won’t even take his own side in an argument.

What appears to be a new approach toward free speech is codified in the A.C.L.U.’s “case selection guidelines” promulgated in 2018. In determining what First Amendment cases to take, the organization will now consider “factors such as the (present and historical) context of the proposed speech; the potential effect on marginalized communities; the extent to which the speech may assist in advancing the goals of white supremacists or others whose views are contrary to our values; and the structural and power inequalities in the community in which the speech will occur.” Elsewhere, the document speaks of the “serious harms” certain speech can inflict upon “marginalized” people, the sort of therapeutic language used to justify the patently unconstitutional “hate speech” prohibitions the A.C.L.U. historically opposed. What this all portends is that the A.C.L.U. will be less likely to defend the speech of which its largely progressive membership disapproves.

The 2017 Unite the Right rally in Charlottesville, Virginia. In the wake of the violence, several chapters of the A.C.L.U. announced that they would no longer defend white supremacists.

Such a sentiment would appall the A.C.L.U.’s founding generation. In their 1934 pamphlet defending the free-speech rights of Nazis, they posed the question that must perennially be put to those who claim to believe in liberty but nonetheless advocate limiting it for individuals they don’t like: “Where do you draw the line?” Such people always answer “in the terms of revolutionists—at our political enemies.”

What’s going on inside the A.C.L.U. is indeed a revolution, as progressives hostile to the nonpartisan defense of civil rights and civil liberties overthrow the liberal Old Guard that founded and ran the organization for nearly a century. More pressing for this new constituency than robust defense of the First Amendment is tweeting support for “men who get their periods.” Like many in the Trump era, the A.C.L.U. has lamentably responded to the president’s innumerable moral deficiencies, ethical outrages, and abuses of power by eschewing its own principles.

What this all portends is that the A.C.L.U. will be less likely to defend the speech of which its largely progressive membership disapproves.

The proximate cause of this shift—and, I suspect, the reason why there is no tribute to Skokie in this volume—was the outrage many of the A.C.L.U.’s staff and members expressed when it defended the organizers of the 2017 Unite the Right rally in Charlottesville. The murder of counterprotestor Heather Heyer by a neo-Nazi was both a tragedy and a crime—one that I hasten to point out is not protected by any interpretation of the First Amendment. Yet to a rising generation of progressives who conflate speech and violence, such distinctions are bourgeois legalisms that the powerful use to oppress the powerless.

Lawyer Clarence Darrow, a prominent member of the A.C.L.U., during the 1925 Scopes “Monkey Trial.”

The transformation of the A.C.L.U.—once a group that proudly welcomed liberals, conservatives, radicals, and libertarians under its big tent—can also be ascribed to the broader polarization blighting every corner of American society. In the wake of Trump’s election, membership quadrupled and donations increased by an even greater factor. Ayelet Waldman, who co-edited Fight of the Century with her husband, Michael Chabon, said that inspiration for the book came from her need to do “something, anything” in protest of Trump’s election. “It’s hard as a writer to know how to resist.” But what’s good for an organization’s bottom line isn’t always synonymous with what’s good for its mission. Especially an organization which purports to be nonpartisan.

Many of the A.C.L.U.’s new supporters see the group not as a politically independent custodian of the Constitution, but just another front in the #resistance fighting the Trump administration. Flattering this constituency with odes to the A.C.L.U.’s defense of the high-school students who donned black armbands in protest of the Vietnam War, or the African-American bus driver who set an American flag alight after the shooting of civil-rights activist James Meredith, is easy. More challenging, but also more constructive, would have been an essay on the group’s 1960 decision to sue the New York City parks commissioner, a former New York Civil Liberties Union board member, so that American Nazi Party leader George Lincoln Rockwell could hold a rally in Union Square. In so doing, Neier writes, the A.C.L.U. was “suing a friend on behalf of an enemy.” Sometimes that’s what protecting freedom demands. The cause of free speech in this country will be in serious trouble if its defense is left to such fair-weather friends.

James Kirchick is the author of The End of Europe: Dictators, Demagogues, and the Coming Dark Age