Calling Donald Trump a "clear and present danger," scholars and civil rights advocates on Friday urged Facebook to permanently ban the former US president from the platform.

Critics of the social media company along with strong advocates of unfettered political discourse called on Facebook's oversight board to endorse the decision to boot Trump from the platform in the aftermath of the January 6 attack on the US Capitol.

A public comment period ended Friday with more than 9,000 submissions regarding the case, according to the board. The social network itself has asked the independent body to review Trump's eviction from the online community.

The oversight board has the final say on what is removed or allowed to remain on the world's biggest social network.

A ruling is expected by April.

"Overturning the Trump ban is an invitation to violence, hate and disinformation that will cost lives and undermine democracy," a group of critics maintained in a letter. "Don't strike the match."

They described Trump as a serial abuser of social media rules who poses a danger "to democracy and human life."

Signers of the letter include Rashad Robinson, president of Color of Change; Anti-Defamation League head Jonathan Greenblatt; and Harvard professor Lawrence Tribe.

Conservatives on Capitol Hill and beyond say the moves by Facebook and Twitter to "deplatform" Trump demonstrate political bias and inhibit free speech.

Twitter chief Jack Dorsey last month backed the messaging platform's ban of Trump, but said it sets a "dangerous" precedent and represents a failure to promote healthy conversation on social networks.

"Having to ban an account has real and significant ramifications," Dorsey said in a string of tweets about his take on the company's decision to permanently bar the president.

"While there are clear and obvious exceptions, I feel a ban is a failure of ours ultimately to promote healthy conversation."

Supporters of Donald Trump erected a makeshift gallows near the US Capitol on January 6
Supporters of Donald Trump erected a makeshift gallows near the US Capitol on January 6 AFP / Andrew CABALLERO-REYNOLDS

Trump's access to social media platforms that he used as a megaphone during his presidency has been largely cut off since a violent mob of his supporters stormed the Capitol in Washington.

Twitter recently announced that Trump will not be permitted back on the network he used constantly, even if he runs for office again.

"Our policies are designed to ensure that people are not inciting violence," Twitter Chief Financial Officer Ned Segal said on CNBC.

Even German Chancellor Angela Merkel has weighed in, stating through her spokesman that she believed freedom of opinion should not be determined by "the management of social media platforms."

A group of US university law professors, joined by former Facebook security chief Alex Stamos, sent the board a letter reasoning that while a disfavored "last resort," the removal of Trump from the social network was justified by his actions.

"The eventual deplatforming of Trump's accounts helped defuse a dangerous and antidemocratic situation," read the letter, sent by University of California law professor Richard Hasen to speak for the group.

"Had the platforms granted Trump continued, broad unmediated access, he could have provoked additional violence and potentially further undermined the peaceful transition of power which is essential to a working democracy."

In its letter to Facebook's board, the activist group also lambasted the social media company for employing the board as a "fig leaf" to evade responsibility for tough decisions and called for laws regulating social media giants.

The board has stressed its independence, citing funding by an irrevocable trust set up by Facebook, and makes policy recommendations along with binding rulings on specific appeals.

Members of Facebook's oversight board come from various countries and include jurists, human rights activists, journalists, a Nobel peace laureate and a former Danish prime minister.

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