By Deepa Seetharaman and Jeff Horwitz 

Facebook Inc. Chief Executive Mark Zuckerberg, addressing employees in a highly charged town hall meeting Tuesday, defended his decision to preserve posts on the platform by President Donald Trump despite mounting outrage from insiders and civil rights activists that one of his messages last week was tantamount to a call for violence and therefore a violation of the company's rules.

The employee meeting, initially scheduled for Thursday, came a day after hundreds of employees participated in a "virtual walkout" opposing the policy decision, with several airing their grievances with the company publicly on Twitter. Two software engineers publicly said on Monday they quit the company, in part due to Facebook's failure to enforce its own rules when it comes to Mr. Trump.

The meeting wasn't streamed publicly, as some internal Facebook events have been recently, but employees said Mr. Zuckerberg didn't give ground on the issue. He has said he doesn't believe private companies should regulate political speech and that while he personally found Mr. Trump's posts "deeply offensive," he thinks it is better for the debate over his comments to be held publicly than suppressed.

"It's crystal clear today that leadership refuses to stand with us," said Brandon Dail, a Facebook engineer, in a Twitter post.

In posts on Twitter and Facebook on Friday, Mr. Trump called demonstrators thugs and warned: "When the looting starts, the shooting starts." Twitter shielded the message from public view, while Facebook took no action.

The employee turmoil amounts to one of the toughest challenges to Mr. Zuckerberg's leadership in the last 16 years. Since late last week, Mr. Zuckerberg and Chief Operating Officer Sheryl Sandberg have discussed the policy decision with employees, especially black executives and employees within the company, as well as civil rights leaders. Those meetings, some of the participants said, were largely unsatisfying.

Three civil rights leaders -- Vanita Gupta, president and CEO of The Leadership Conference on Civil and Human Rights; Sherrilyn Ifill, president and director-counsel of the NAACP Legal Defense and Educational Fund, Inc.; and Rashad Robinson, president of Color of Change -- issued a fiery statement after speaking with Mr. Zuckerberg and Ms. Sandberg late Monday.

"We are disappointed and stunned by Mark's incomprehensible explanations for allowing the Trump posts to remain up," they said. "He did not demonstrate understanding of historic or modern-day voter suppression and he refuses to acknowledge how Facebook is facilitating Trump's call for violence against protesters. Mark is setting a very dangerous precedent."

Write to Deepa Seetharaman at Deepa.Seetharaman@wsj.com and Jeff Horwitz at Jeff.Horwitz@wsj.com

(END) Dow Jones Newswires

June 02, 2020 16:10 ET (20:10 GMT)

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