O'Reilly has said NBC News, as an organization, has gone sharply to the left. He cited the network's decision last fall to begin referring to the sectarian violence in Iraq as a civil war, a phrase the Bush administration has resisted.
He made his displeasure clear in a recent interview with NBC's Andrea Mitchell, then later talked to a body language consultant who said Mitchell looked uncomfortable.
"I think it's really kind of sad and pathetic, some of the things that he's been lobbing at us these days," Capus told reporters Wednesday. "I don't quite understand it. I assume it's because Keith Olbermann has had such tremendous growth and there's real momentum behind Keith's broadcast."
David Tabacoff, executive producer of FOX News' "The O'Reilly Factor," said Thursday in a statement, "It's nice to see that Jeff Zucker let Steve off his leash for a few minutes, but what is it about being exposed as a liberal news organization that he finds sad and pathetic?"
Zucker is chief executive of NBC Universal's television group.
O'Reilly has long been the ratings leader in cable news. But Olbermann, who has stepped up commentary criticizing President Bush in the last five months, has seen some ratings growth opposite O'Reilly.
As O'Reilly has been criticizing NBC, prime-time host Joe Scarborough of MSNBC has criticized him, making O'Reilly a frequent topic on the MSNBC program.
"As far as I'm concerned, he's not commenting on NBC News," Capus said. "He's just trying to do this personal feud. The more he does it, the more success we have, so he can do it anytime he wants, as far as I'm concerned. And I think the audience knows exactly what's at play here."