While strolling through the graceful town of Bellagio, Italy, on a bright summer morning in 2014, I stopped at an A.T.M. On a nearby restaurant patio, belonging to one of the grand lakeside hotels packed with tourists, I noticed an older man staring at me. Upon tendering my cash, I turned around to meet his glare. He pointed a finger at me and said, “Hey. You. I recognize you.” I was certain that he did not. He removed his sunglasses, and, with a bit of a grimace and a snort, he announced, “You’re the liberal—on ‘O’Reilly’ !”

I walked the few feet to his table and introduced myself. The fellow, from Michigan, was so tickled to have spotted someone from his beloved show at a cash point in Italy. I snickered at my own sad predicament. I’ve spent my life trying to be as deeply learned as I can—humanities research had brought me to this beautiful spot—and, lo and behold, my one nod of recognition that morning was as a left-wing mouthpiece on Fox. In subsequent years, when O’Reilly fans would stop me, almost always in nonpartisan tourist spaces (Times Square, airport lounges), I ceased being surprised: O’Reilly viewers were so fanatical that they could identify even his random, infrequent guests.

I have always believed that coastal leftists need to step outside of our political and social comfort zones. In that spirit, I agreed to appear on “The O’Reilly Factor” five years ago with the strategic, if idealistic, calculation that roughly a quarter of O’Reilly’s viewership had to be apolitical, moderate, and persuadable by fair-minded analysis. I typically appeared on the show to discuss heated economic and political topics: raising the minimum wage, the demands of Occupy Wall Street, police brutality, Stand Your Ground gun laws, and similar issues. Truth be told, early on, for left-wing mischief-makers, O’Reilly was like that beast you saw on safari—you wanted to shoot it and hang it as a trophy. Once, after I posted on Twitter about my imminent appearance, a longtime friend of mine texted, “Jealous. My Mitty fantasy is to spar with that bastard. Good luck!”

I would appear on “The O’Reilly Factor” from its New York City studio, with O’Reilly sitting just feet from me, pancaked in makeup, stiff as a mummy. O’Reilly pioneered the gimmick now favored by other Fox hosts: pose a basic, neutral-sounding question and, as soon as an answer rolls from an opponent’s tongue, immediately interrupt and ask a more hostile, complicated question. O’Reilly hoped that “stepping on” your answer right out of the gate would scramble your train of thought. As O’Reilly’s opponent, you had to box with him aggressively to honor the viewpoint that you were defending yet be careful not to ridicule him too blatantly and risk alienating his viewers. Of course, the show was jerry-rigged to flatter its host and entertain its fans. But, despite my disgust with the format and with Fox in general, I felt that if I could get a sizable slice of O’Reilly’s viewership to think fairly, for a few moments, about undocumented immigrants, corporate wage theft, or police brutality, my time would be well spent.

O’Reilly pretended to hate “identity politics,” but his show was often a David-and-Goliath melodrama of identity politics, placing him and his right-wing viewers in the David role, as aggrieved victims of political correctness, as the industrious bootstrappers, and so on. In one of our encounters, we debated a strike among fast-food workers. O’Reilly boasted, “My first job was at a Carvel ice-cream stand. I was paid minimum wage. . . . I understood that I was a rookie in the labor force and could get a recommendation from my future boss, so I didn’t complain about the low pay. The next summer, before I went to college, I took a Red Cross course. I got my lifeguard certification and became a water-safety instructor. Immediately, I made five times more money than I made at Carvel.”

Struggling not to roll my eyes, I told Bill that he was living in the past. I informed him that most minimum-wage workers these days are not seventeen-year-old students on summer break. Two-thirds of the current minimum-wage work force consists of women, with a median age of thirty-two. “I wish we could go back to that economy where the middle class wasn’t hollowed out,” I told his viewers. “But, over the last couple of decades, we’ve seen workers work harder without being rewarded. These workers are wise to strike; I don’t know anyone who can live on $7.25 an hour.” Thanks to such a low minimum wage, many fast-food workers qualify for programs like Medicaid, energy assistance, and food assistance for children. Welfare is often a supplement to their hard work, not a substitute. In these and other matters, O’Reilly pretended to be a populist but he really favored corporate interests, especially big-box retailers and fast-food titans. That’s why I find it especially delicious that a multi-billion-dollar corporation glanced at its bottom line and fired him.

The most caustic exchange I ever had with O’Reilly occurred when he invited me to discuss an Op-Ed that I had written for the Times. In that piece, I lamented that Trayvon Martin had been murdered by George Zimmerman “in cold blood.” O’Reilly had been a vehement apologist for the youth’s killer. Our interview, ostensibly, was to center on Zimmerman’s trial, but O’Reilly’s hidden agenda was to shame me into taking my assertion back and to apologize to Zimmerman. I refused. I insisted that the black young man had in fact been murdered “in cold blood.” I reminded O’Reilly that Zimmerman was an unknown, suspicious-looking adult, and that Trayvon was just a teen-ager who deserved to be treated with dignity, especially as a minor. Outraged, Bill shouted, “I don’t care if he was four years old!” There I sat, feet from O’Reilly and his world view: everyone should have a gun to defend himself, and the right to use it, even if a four-year-old is involved; and a vigilante’s right to life supersedes that of an innocent black teen’s.

I could gauge the quality of my performance on “The O’Reilly Factor” by the response from viewers. When I received no response, I knew my efforts had fallen flat. In other instances, just minutes after wrapping up an appearance, my inbox would be flooded with choice feedback from his fans: “Commie,” “Nigger,” “Buckwheat,” “Fag.” These sorts of e-mails, combined with a a series of hot, angry tweets, were an accurate measure of an effective appearance. In the thin-skinned ethos of O’Reilly’s right-wing universe, the more you battered its poster boy with dead-on punches, the more ferocious the vitriol directed at you.

The intimate rapport O’Reilly developed with his followers sometimes transferred to his guests. Some fans pried into my life, asking personal questions. They opened up their lives to me by e-mail, sharing affecting accounts of their workplaces, homes, backgrounds, and challenges. Many e-mails from O’Reilly fans, whether I agreed with their conclusions or not, offered thoughtful, useful insights into this country’s predicaments. They showed me the blind spots in my understanding of contemporary America—particularly how people’s experiences, their class, and (usually) their whiteness shapes their public-policy perceptions. I credit O’Reilly’s popularity to his fortunate timing. As legions of disaffected white Americans struggled with the economic, political, and demographic changes convulsing America, O’Reilly offered himself as a comrade and ringleader to shepherd them through.

There is a hopeful lesson from O’Reilly’s comeuppance: the right mix of political and legal action, investigative journalism, and business scorn can deliver even the most powerful tyrant a stinging rebuke. O’Reilly and the former Fox C.E.O. Roger Ailes might be out the door because of the harassment charges levelled against them, but that leaves their angry network intact, still as comfortable as ever to crap on the environment, women, immigrants, black people, transgender people, scientific research, and anything smacking of progress. The fight is still on to persuade those members of Fox Nation who are willing to listen. Even though O’Reilly has been dislodged, his network, left unchanged, can always grow a new figurehead, hydra-like, in his place.