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Fox News correspondent at-large Geraldo Rivera on Thursday apologized for discounting claims of sexual harassment made by former network anchor Gretchen Carlson and others against ex-CEO Roger Ailes.

Two days after Rivera defended Ailes in a tweet, "it became apparent that Gretchen was not alone in alleging abhorrent behavior behind his closed doors," Rivera wrote on Facebook. "Now I am filled with regret for stubbornly discounting their various allegations."

Ailes, who is credited with turning Fox News into a media powerhouse over two decades, stepped down from his position in July after Carlson filed a lawsuit in which she claimed Ailes had sabotaged her career after she rejected his sexual advances.

Ailes has denied the claims.

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"I apologize for my skepticism. Like victims of sexual assault, those alleging harassment deserve the presumption of credibility," Rivera wrote.

Rivera said he initially discounted the claims from Carlson and other women who came forward because the alleged actions did not match the man he knew. "Like virtually all my colleagues at Fox News, I was totally blindsided by his sexual harassment scandal, which is why I responded to Gretchen Carlson’s initial filing of her lawsuit with extreme skepticism," he said.

I've known him 40 years. He's about as flirty as the grizzly in #TheRevenant. I stand with Roger Ailes — Geraldo Rivera (@GeraldoRivera) July 13, 2016

"The man we knew as the blustering genius who invented our mighty Fox News Channel is a deceitful, selfish misogynist, if the charges against him are true," Rivera said. “And if they are true, then his shame and banishment are well earned."

Related: The Next Generation of Murdochs Steps Up at Fox

The parent company of Fox News, 21st Century Fox, said Tuesday it reached a settlement with Carlson. The terms of the deal were not disclosed.

According to Vanity Fair, which first reported news of the settlement, Fox has agreed to pay Carlson $20 million.

Rivera also said in the post that the Ailes scandal has resulted in a planned book being canceled.

Rivera said publisher HarperCollins chose not to publish his memoir, titled "Geraldo of Arabia, From Tora Bora to Trump," due to his "uninformed support" of Ailes and "relatively flattering portrayal of him" in an early manuscript.

Rivera also apologized to New York Magazine writer Gabriel Sherman, who wrote extensively about the matter and whom Rivera had called a "nerd with a grudge" as the scandal unfolded. "He is on the right side of history," Rivera said.

"To all the victims of sexual harassment, direct and indirect, I am sorry for what happened to you" Rivera said. "As the father of three daughters, including one in the news business, I urge all who have been offended to reach out. Similarly, if you see harassment, say harassment, even if the alleged offender is an old friend."