Facebook chief executive Mark Zuckerberg has defended his decision not to interfere with posts by US President Donald Trump, US media reported, after the social media giant's hands-off policy sparked outrage and prompted some employees to quit. Social media platforms have faced calls to moderate the president's comments, most recently because of the unrest gripping America after an unarmed black man's death during arrest as a white policeman knelt on his neck. The row began last week when Mr Zuckerberg said Facebook would not remove or flag Mr Trump's posts that appeared to encourage violence against those protesting police racism, even as social media platform Twitter put warning labels on some of the president's tweets over accuracy issues or the glorification of violence. Mr Zuckerberg told employees in a video conference on Tuesday he spoke to Mr Trump on the phone after the decision, and that he "used that opportunity to make him know I felt this post was inflammatory and harmful, and let him know where we stood on it", <em>The New York Times</em> reported, citing a recording of the call. The chief executive was referring to a post by the president that said "when the looting starts, the shooting starts" – the same comment on Twitter was still visible but behind a warning label. Mr Zuckerberg explained his reasoning in a Facebook post on Friday, a position he has since reiterated several times. “I know many people are upset that we’ve left the President’s posts up, but our position is that we should enable as much expression as possible unless it will cause imminent risk of specific harms or dangers spelled out in clear policies,” Zuckerberg wrote. Facebook's move prompted intense scrutiny and dissent from employees, and it was a "tough decision" over content that had upset him personally, Mr Zuckerberg told about 25,000 staff who tuned in yesterday, according to the tech website <em>Recode,</em> which had obtained a copy of the call. "I knew that the stakes were very high on this, and knew a lot of people would be upset if we made the decision to leave it up," Mr Zuckerberg said on the call, not backing down from the policy. The call came after a number of Facebook employees publicly expressed their anger at the company's policy on incendiary content, with many quitting or threatening to leave. Mr Zuckerberg had not kept his word about stopping posts that glorify violence, said Timothy Aveni, a software engineer who resigned from the company. "Facebook will keep moving the goalposts every time Trump escalates, finding excuse after excuse not to act on increasingly dangerous rhetoric," Mr Aveni wrote on his Facebook page. Prior to the staff call, civil rights activists had strongly criticised Facebook's policy. "We are disappointed and stunned by Mark's incomprehensible explanations for allowing the Trump posts to remain up," said a statement from three leaders: Vanita Gupta of the Leadership Conference on Civil and Human Rights, Sherrilyn Ifill of the NAACP Legal Defence and Educational Fund, and Rashad Robinson of Colour of Change. "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 for other voices who would say similar harmful things on Facebook."