Sure, I’ll go on your show! Just not with that guy.

More than 20 years ago, as the first intifada was just beginning, two lowly staffers at ABC were assigned the task of getting some Israelis and Palestinians to appear together on a special episode of Nightline to be taped in Jerusalem. Planning was a disaster. Riven by infighting, Palestinians kept objecting to their fellow panelists and dropping out. Meanwhile, the Israelis refused to talk to anyone associated with the PLO, which ruled out just about every Palestinian panelist. Eventually, a compromise was struck: The Palestinians gave up their demand that an actual piece of barbed wire be strung between them and the Israelis (they settled for a wall), and the Israelis relented on their refusal to address the Palestinians directly. Everybody won: Both groups got their messages across, and the special was a hit.

Which raises the question: If producers can get two warring sides in a bloody and emotional regional war to talk to each other, why is it so hard to get some guests to appear together on TV?

Gore Vidal once said, “Never pass up a chance to have sex or appear on television.” But in both cases, it really depends with whom. There are some guests who simply refuse to go on the air with other particular people or with anyone at all. Likewise, there are some people who no one else wants to appear with. It’s rarely discussed, because the bookers who mediate these ego wars are bound by contract—and their own interests—to keep quiet. And hosts rarely mention the snubs on-air, since they want guests to come back. But snubbing happens all the time, and conversations with bookers, producers, and guests reveal that some divas are especially notorious.

The biggest offenders are usually the ones whose egos are too big to accommodate any company: Henry Kissinger, Zbigniew Brzezinski, Alexander Haig, and others who figure they have better uses for their time than debating some flack on the air. “They would only go on if they could do the show alone,” says a former producer for Crossfire. “Brzezinski won’t debase his cable currency by being a two-box,” explained a current booker, referring to the practice of displaying guests on a split screen. Another booker cited Brzezinski’s refusal to go on with Pat Buchanan—”probably because he thinks he’s an anti-Semite.” (An assistant to Brzezinski says: “It isn’t true that he will only appear alone. He has appeared many, many times with other guests.” Maybe so. But bookers say he doesn’t do so willingly.)

Senators also tend to be finicky when it comes to sharing air time. Such was the case during the Democratic National Convention, when Sen. Chuck Schumer threw a fit upon learning that he would have to appear on The O’Reilly Factor with Clinton lawyer Lanny Davis. (Schumer had been told he’d be appearing alone.) When Davis refused to back down—”Unless Roger Ailes calls me personally, I’m doing the show”—they appeared together.

The food chain continues. Senators don’t go on with members of the House, who in turn won’t appear with anyone other than elected officials of their rank or higher. So why did Howard Dean refuse to debate his Republican counterpart, RNC Chairman Ken Mehlman, on the Today show in 2006? Host Meredith Vieira called Dean out on the air. Part of the reason was simply airtime, a Democratic spokeswoman explained; you can’t say as much when you’re on with someone else. But it’s also a stature issue. Both were chairman of their respective parties, but Dean was a former governor while Mehlman was simply a former campaign manager (albeit a victorious one—something Dean didn’t have on his résumé). “You don’t want to put your boss on with Joe Schmo,” the spokeswoman said while stressing that she was not comparing Mehlman to Mr. Schmo.

In other cases, guests will refuse to appear as an act of protest. After Don Imus called members of the Rutgers women’s basketball team “nappy-headed hos,” Cal Ripken canceled his appearance on Imus’ show. John McCain pulled a similar stunt with Larry King, canceling his appearance in protest not against bigotry but against journalism itself: Earlier that day, CNN’s Campbell Brown had raked a McCain spokesman over the coals on the question of Sarah Palin’s foreign-policy experience.

Other guests will turn down appearances because of another person’s political beliefs. To speak with them, in their view, is to dignify them. Representatives of People for the Ethical Treatment of Animals won’t go on the air with Washington lobbyist Richard Berman, who has accused PETA of euthanizing animals. Nor will most major unions, given Berman’s anti-union lobbying. (The AFL-CIO once sent a written statement criticizing Berman in lieu of appearing on CNBC.) Likewise, doctors’ organizations will often refuse to appear with paranoiacs who say vaccinations cause autism.

Some guests will turn down appearances with Daniel Pipes, the notorious Israel hawk; same with University of Chicago professor Ali Abuminah, who supports Palestinian causes. Neither is known for his rhetorical restraint: A head-to-head matchup between the two on BBC Radio once resulted in an on-air meltdown.

Sometimes the refusal is rooted in a perfectly understandable instinct for self-preservation. “Some people won’t go on with [Alan] Dershowitz,” says one booker. “You don’t want to have your ass kicked.” Hosts can be intimidating, too. Michael Kinsley, a former Crossfire host and Slate founder, said some guests wouldn’t go on with co-host Pat Buchanan: “Not even on alleged principle. Most of the time it was because they were scared. He was very good.” Same with former Soviet spokesman Vladimir Posner, who became famous in the late 1980s as the Soviets’ most articulate, handsome, and—crucially—accent-free advocate. “I had one or two administration foreign-policy experts who refused to go on with him,” says Gil Pimentel, who produced Nightline.

Self-preservation can also take the form of not wanting your opponent to raise embarrassing issues. Ann Coulter once vetoed a CNN appearance because another guest, Air America host Sam Seder, was likely to mention a controversy over Coulter allegedly voting in the wrong precinct. (Seder was booted in favor of Slate’s Mickey Kaus.) Likewise, Jane Hamsher of Firedoglake was slated to speak last month with the New Republic’s James Kirchick about Sen. Joe Lieberman on the NPR show To the Point. But in the end, Hamsher appeared alone while Kirchick spoke separately with a third guest, Ed Kilgore. Hamsher had apparently objected to going on the air with Kirchick, who often reminds readers and listeners about the time Hamsher digitally altered a picture of Joe Lieberman to make him appear in blackface. (Hamsher denied the entire radio incident.)

Raising past embarrassments can be an effective negotiating tool. The best way to end an O’Reilly segment: Say the word loofah. (If only Hendrick Hertzberg had known.)

In many cases, the objection is personal. You have to be careful booking guests who don’t like each other. Ill-advised pairings that come to mind: former Bush spokesman Scott McClellan and Karl Rove; former Bush loyalist Matthew Dowd and Karl Rove; former Bush Treasury Secretary Paul O’Neill and Karl Rove. “You’d have to have the deft touch,” recalls former Good Morning America producer Heidi Berenson. “Either to put them in different locations, or pre-tape one, or scurry one down the hallway. Sometimes it turned into a covert operation.”

Then there’s a category all its own: Coulter. Lanny Davis will not go on the air with Coulter, period. “The last time I was on with her,” he said, “she was so venomous and vindictive and hateful … I literally went home and took a shower.” Indeed, Coulter’s name came up more than anyone else’s as the most objectionable co-guest. “She’s just ruthless,” says one booker. “She filibusters. There’s no nuance, there’s no hope.” Hosts are no warmer: There are probably fewer shows that will have her on than won’t.

Coulter herself doesn’t understand why. “I never insult guests personally or talk over them the way they do to me, so anyone who won’t go on with me is just being a pussy,” she wrote in an e-mail. Into that category fall Anderson Cooper, who won’t have her on his show, and Elizabeth Holtzman, who Coulter says “stormed off” the set of Hannity and Colmes during a discussion of the Clinton impeachment in 1998. (“I believe in reasoned discourse,” Holtzman told me, “not screaming.”) “I can see why Anderson Cooper won’t have me on—let’s be honest: I’m pretty sure I could take him,” Coulter wrote to me. “But what about the rest of them? Are they all afraid of a 99-pound woman in a mini-skirt?” (Of course, Coulter is not guilt-free when it comes to storming off sets.)

Most of the time, though, guests aren’t even aware of their snubbing. “I’m sure it has happened,” says columnist and Morning Joe regular Mike Barnicle. “The producers probably feel so badly for me, they never tell me the people said, ‘Fuck no.’ “