Earlier, a Facebook whistleblower Frances Haugen told US lawmakers Tuesday that the social media giant fuels division, harms children and urgently needs to be regulated, drawing pledges Congress would take up long-delayed action.
Haugen testified on Capitol Hill after she leaked reams of internal research to authorities and The Wall Street Journal.
"I believe that Facebook's products harm children, stoke division and weaken our democracy," Haugen told a Senate panel.
In her testimony, she emphasised the power held by a service that is tightly woven into the daily lives of billions of users.
She also noted the risks that the social media giant's platforms are fueling a contagion of eating disorders, body-shaming and self-dissatisfaction that is particularly dangerous for young people.
Zuckerberg denied all the claims in a note to Facebook employees that he posted on his account, calling the argument that the company pushes content that makes people angry for profit "deeply illogical."
"We make money from ads, and advertisers consistently tell us they don't want their ads next to harmful or angry content. And I don't know any tech company that sets out to build products that make people angry or depressed. The moral, business and product incentives all point in the opposite direction," he said.