Speaking with reporters on Thursday during a media briefing, Zuckerberg explained his surprise with the report’s allegations that the Definers public relations firm, working on behalf of Facebook, performed a number of controversial services intended to deflect attention away from Facebook during a time of tremendous turmoil for the once Silicon Valley darling.

Among some of Definers’ PR tactics included seeding negative articles about Facebook’s rivals like Apple and attempting to convince reporters to link an anti-Facebook activist group with the liberal billionaire George Soros, the Times report detailed. After hiring the firm, Facebook also allegedly lobbied for a sex-trafficking act that the firm thought would help the company rebuild trust with lawmakers, the Times report detailed.

“I learned about this relationship when I read The New York Times piece yesterday,” Zuckerberg said. “As soon as I read it, I said this isn’t the type of firm we want to be working with and we stopped working with them.”

He added that the firm’s tactics “might be normal in Washington, but it’s not something I want Facebook to be associated with.”

Zuckerberg also provided cover for Facebook Chief Operating Officer Sheryl Sandberg, who he said was also not involved with Definers’ controversial tactics, and that she learned of them at the same time he did.

“Overall Sheryl is doing great work for the company,” Zuckerberg said. “She has been a very important partner to me and will continue to be.”

Regarding Soros, Zuckerberg said he has “tremendous respect” for the activist financier.

Zuckerberg said that “someone on our communications team” hired Definers, but declined to comment whether anyone would be fired for enlisting its services. He said that it was under his “understanding” that Facebook didn’t hire the PR firm to “attack any competitors or something like that.”

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The Facebook CEO also said that unspecified employees told him that it wasn’t true that the Definers group was spreading misinformation. When a reporter pointed out the irony of Facebook using Definers’ opposition research tactics while the company itself is attempting to stop fake news and propaganda from spreading on its social networking service, Zuckerberg brushed it off and said “From what I can tell, that isn’t true.”

“I don’t think the analogy you are making makes any sense,” Zuckerberg told the reporter.

Update: 8:00 PM PST to add Sandberg’s comments and to clarify that Facebook engaged in lobbying, and not Definers.

Sandberg posted her own comments later in the day regarding the firm:

We’re no longer working with them but at the time, they were trying to show that some of the activity against us that appeared to be grassroots also had major organizations behind them. I did not know we hired them or about the work they were doing, but I should have. I have great respect for George Soros – and the anti-Semitic conspiracy theories against him are abhorrent.