One of my least favorite modern phrases is “gets it.” So-and-so “gets it,” and so-and-so “doesn’t get it.” But sometimes I find the phrase handy. And David Horowitz gets it. Gets what?

Well, many things, but he certainly gets the Left, from which he comes. As readers of this magazine don’t need to be told, Horowitz made one of the most famous, and consequential, journeys from left to right in recent history. He knows the Left from the inside out. He has their number, as we used to say. (“Gets it,” frankly, was sexual.)

Abigail Thernstrom is another intellectual who traveled from left to right. During the 1990s, she told me that she’d had an interesting conversation with an academic associated with the Clinton administration. He said that he would no longer engage in public debates with her. Why? “Because, Abby, you know what I’m going to say before I say it, and you know why I’m going to say it.”

Any leftist who debates David Horowitz is taking his life into his hands. Maybe that’s why so few agree to do it.

Horowitz is embarked on a tremendous publishing project: The Black Book of the American Left: The Collected Conservative Writings of David Horowitz. I remember how glad I was in 1997 when The Black Book of Communism came out. It documented the crimes of that gang, worldwide. In his collection, Horowitz is now up to Volume V, headed “Culture Wars.”

The volume is organized in five parts: “The Progressive Party Line”; “Media Culture”; “Sexual Politics”; “Feminist Assaults”; and “The Government’s Left-wing Network” (i.e., public broadcasting). It all begins with an introduction by Horowitz, which is worth the price of admission alone.

In this introduction, Horowitz says that Antonio Gramsci, the Italian Communist, had an idea: Forget trying to take over the means of industrial production; instead, take over the means of cultural production. “In Gramsci’s conception,” writes Horowitz, “this meant infiltrating and then subverting universities, churches, media and the institutions of the arts.”

I am both a political journalist and a music critic, and sometimes musicians come out to me — that is, they confide to me that they are conservative. “Don’t tell anyone!” they make me swear. “If it were known that I lean right, I’d be in big trouble. I could even be fired.” Really? Why should it matter to an orchestra whether an oboist voted for Romney or Obama? In any event, it does. And the Romney voter had better keep her mouth shut.

“In Gramsci’s vision,” Horowitz later says, “radical subversion of these institutions and therefore of the culture would make radical ideas the ruling ideas, which would result in radicals’ becoming a political ruling class.” That’s what has happened, right?

The campuses are now erupting in political correctness, which is really too benign a term for the phenomenon. I’ll let Horowitz speak to the matter:

The phenomenon of “political correctness” is, in fact, an updated version of the “party line” — a stock feature of the organizations of the Communist-progressive left. The utility of a party line lies in the way it demonizes opponents, converting dissent into deviancy, while requiring its adherents to reduce complex realities to political formulas, which deprives them of the ability to learn from their experiences.

A neater description of the campus situation, I can hardly imagine. A few weeks ago, a Yale official apologized abjectly to students for offenses that the students had simply made up. I thought, “Oh, my gosh. As in the Cultural Revolution, the adults are afraid of the kids. The adults are trembling.”

Part I of Volume V opens with an essay that Horowitz wrote with Peter Collier, his longtime comrade (on both left and right). “It’s the Culture, Stupid!” the essay is called. They wrote it in late 1992, when the Bush 41 administration was giving way to the Clinton administration. The essay brought to me a flood of memories, and is especially interesting in light of the present day.

Horowitz and Collier discuss Johnnetta Cole, a key figure on Bill Clinton’s transition team. She was a veteran leftist, a robust supporter of Fidel Castro and other Communist dictators. Now she is the director of a Smithsonian museum. Donna Shalala was a similar sort. She had been chancellor of the University of Wisconsin, and, in the Clinton administration, would be the secretary of Health and Human Services. After government, she became president of the University of Miami. Now she is the head of the Clinton Foundation.

In their essay, Horowitz and Collier mention the president-elect’s “promise to lift the ban on HIV-infected Haitians now quarantined at Guantanamo.” In that way did Gitmo once make the news! The authors also say that, with the Cold War won, foreign affairs may be less critical, “at least for a while.” Horowitz and Collier were characteristically wise to include those words. The “holiday from history,” as people called it, ended less than a decade later, on a September day in 2001.

The authors do not fail to reckon with the incoming First Lady, Hillary Clinton — or was she Rodham or Rodham Clinton then? “It is the social agenda that is now at the center of American concerns, and this agenda is in danger of being handed to what we will probably soon be calling the Hillary Left.”

In early 2000, when Hillary announced for the Senate in New York, a journalist friend of mine said to me, “They’re going to be in our faces for the rest of our lives, won’t they be? We will never be rid of them.” He was speaking of the Clintons. I didn’t think it could be true. But maybe it is.

My favorite line of the Horowitz-Collier piece is this, and I bet it will be yours, too: “Hillary makes one wish for a Clintonectomy even before the administration takes power.”

In Part II, about media culture, Horowitz writes of Elia Kazan, the late film director, who “named names” in 1952 — who gave testimony to the House Committee on Un-American Activities. Kazan was a brave man, probably a great man, in addition to being a great filmmaker. Horowitz argues that Kazan endured a blacklist longer than any of the Communists who composed the Hollywood Ten: Thanks to his bravery, his testimony, he was shunned by his natural artistic community.

I had an encounter with Kazan a few months ago. The New York Philharmonic screened his 1954 masterpieceOn the Waterfront, for the purpose of playing the Bernstein score, as the movie unspooled overhead. Before the performance, a man came out and said that we should overlook Kazan’s sin in testifying before HUAC. After all, so much time had passed.

Meanwhile, the Philharmonic’s program notes instructed us that Kazan had “cooperated with dark forces.” Funny how the Communists — the allies, well-wishers, and agents of Josef Stalin — are never the “dark forces.” Just the anti-Communists. Also, the program notes referred to “rabid” anti-Communists. Long ago, Orwell pointed out that no one ever said “rabid anti-Nazi” or “rabid anti-fascist.” Only “rabid anti-Communist.” It’s still true.

At the moment, there is a movie celebrating the life of Dalton Trumbo, one of the Hollywood Ten. He loved Stalin, of course, and he also defended Hitler, as long as the Nazi-Soviet Pact lasted. And after the war, he heralded Kim Il Sung in North Korea. Would Hollywood ever make a movie celebrating the life of Elia Kazan?

In a piece about multiculturalism, Horowitz says something that made me sit up straight:

Like most of the destructive -isms of the 20th century, multiculturalism is an invention of well-fed intellectuals. It did not well up from the immigrant communities and ethnic ghettoes of America as an expression of their cultural aspirations or communal needs.

So true, bracingly true — and it reminded me of something that Thomas Sowell says about income inequality: The only people who care about it are well-fed intellectuals (to borrow Horowitz’s term). The poor don’t give a damn about income inequality. They just want to be less poor, regardless of what those above are making.

In 1992, Horowitz wrote a piece called “Homo-McCarthyism.” So early? Yes, that early, although this kind of McCarthyism would increase. Horowitz notes that Joseph Epstein, the writer, was upbraided by GLAAD, the gay activist group, for saying “homosexual” rather than “gay” or “lesbian.” Two years ago, Maureen Dowd of the New York Times began a column, “I’m worried about the Supreme Court.” Farther down, she quoted a friend of hers, who said, “Scalia uses the word ‘homosexual’ the way George Wallace used the word ‘Negro.’”

Antonin Scalia, one of the most refined and cultivated men alive, as George Wallace? So it is in the mind, or at least the propaganda, of the Left culture warriors.

The final part of Volume V, as I mentioned, is about public broadcasting. And you might wonder why the United States, a liberal republic, should have state media. You might also wonder why they defend, and even glorify, the Black Panthers and other such “political” killers. Horowitz is a master of this kind of analysis.

One of the killers is Assata Shakur, née Joyce Chesimard, who killed a New Jersey trooper — Werner Foerster — in 1973. For several decades, she has been a guest of Castro (and his brother). In 1997, Essence magazine published an interview with her under the title “Prisoner in Paradise.” (“Paradise” was totalitarian Cuba.)

In 2011, President Obama invited the rapper Common to perform at the White House. Police organizations protested — because Common had composed a piece glorifying the killer, “A Song for Assata.” Sample lyric: “All this shit so we could be free, so dig it, y’all.” Obama was deaf to the protests, and hugged the rapper, for good measure.

Speaking of cop-killers, Horowitz notes something that surprised even me: National Public Radio invited Mumia Abu-Jamal to give a monthly commentary. Abu-Jamal is the Philadelphia Panther who in 1981 murdered Officer Daniel Faulkner. He has been behind bars ever since. But he is a “social justice” hero to the Left, very much including NPR, it would appear. But the hiring of Abu-Jamal proved too much even for a softened-up America, and the deal never came off.

Auden called the 1930s a “low dishonest decade.” Since the 1960s, we have had nothing but. I have an octogenarian friend who sometimes asks me, “What has happened to us?” Why has America fallen into illiberalism and self-loathing? David Horowitz explains. It may be painful to read the answer, but he has it.

For some 35 years, he has been screaming at us, “These people really hate you!” (“These people” being the Left.) “They are intent on destroying you. Don’t you realize that?” I realize that, yes, and one of the people who helped me to, many years ago, when I was learning about the world, was Horowitz.

Reading Volume V of his magnificent collection made me sad, for two reasons. First, I thought, “Those who need to read this, won’t. Those who need to know this, won’t. David is preaching to the choir. I wish he could preach to the nation at large.”

But then I remembered that I found him — as I found Norman Podhoretz, Bill Buckley, and many others. No teacher or professor assigned them to me. But I found them. And maybe other people will find David, and these volumes?

The second thing that made me sad was this: Après lui, qui? After David, who? Who gets the Left like this, who has its number, who remembers everything that happened, who remembers where they bodies are buried (literally, in the case of the Panthers’ victims), who will scream at us, when we need screaming? Who? But at least we have The Black Book of the American Left, a repository of vital information and thought, indeed of truth.

Jay Nordlinger is a senior editor of National Review and the music critic of The New Criterion. His most recent book is Children of Monsters: An Inquiry into the Sons and Daughters of Dictators.