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Her comments came after Trump called Karl a "third rate reporter" during a briefing on the coronavirus. Karl had asked the president about an inspector general report raising concerns about the government's response to the coronavirus.
Trump pressed Karl on when the inspector general, Christi Grimm, was appointed. When Karl mentioned that she served in former President Obama's administration, Trump went off on Karl, accusing him of concealing information important to the question.
"I watched that debacle yesterday and I was furious when he called you a third-rate reporter," Behar told Karl on Tuesday.
"I wanted you to say, 'no darling, you are a third-rate president,'" she said. Karl smiled and shook his head. "I want the reporters to call him out on his lying," she added.
"I want the reporters to follow up on questions — and if you can't get a real good answer, the correct answer, I want you all to get up and walk out. That's what I want. Can you do that for me and your fellow Americans who are watching this in horror?" Behar asked Karl.
"I understand what you're saying," Karl responded. "But that's something that I would never do. I think it is my job to report on what is happening there, to ask the questions."
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Karl added that it may be tempting to walk out, but he wasn't focused on the president's insults.
"Look, he can insult me all he wants — I don't care. It doesn't matter. It really doesn't matter," he said. "What matters is getting to the bottom of what is happening with the federal response and how people should be responding to this crisis."
But Behar was adamant that Karl should stand up and call Trump a liar.
"Just say it for us!" she insisted.
Earlier in his interview, co-host Whoopi Goldberg described Karl as a "first-rate" reporter. Karl commented that "sometimes you get the sense that the president thinks every question should start with, 'Why are you doing such a great job, Mr. President.'"