“You want free speech?” Mark Zuckerberg posted to Facebook on Thursday.

But it was not one of his many recent speeches and testimony on the importance of freedom of expression. Instead, the Facebook CEO was responding to Aaron Sorkin using his own words from the movie The American President.

Sorkin, who is also behind the Mr Zuckerberg-centred film The Social Network, accused the CEO of “assaulting truth” and hiding behind the guise of protecting free speech by refusing to remove false political advertisements.

“Right now, on your website, is an ad claiming that Joe Biden gave the Ukrainian attorney general a billion dollars not to investigate his son,” wrote Sorkin. “Every square inch of that is a lie and it’s under your logo. That’s not defending free speech, Mark, that’s assaulting truth.”

Facebook birthday: 15 defining moments for the social network Show all 15 1 /15 Facebook birthday: 15 defining moments for the social network Facebook birthday: 15 defining moments for the social network Facebook is born On 4 Feb, 2004, 19-year-old Harvard student Mark Zuckerberg launched a website called 'TheFacebook' from his dorm. Within 24 hours the college social network had more than 1,000 users Wikimedia Commons Facebook birthday: 15 defining moments for the social network Winklevoss twins sue Zuckerberg Within one week of launching, fellow Harvard students Cameron Winklevoss, Tyler Winklevoss and Divya Narendra accused Zuckerberg of stealing their idea. It would be four years later when the resulting lawsuit was finally settled Facebook birthday: 15 defining moments for the social network Open for business The social network finally opened it platform to everyone on 26 September, 2006. The move proved the catalyst in supercharging the site's already explosive growth PA Facebook birthday: 15 defining moments for the social network Billion-dollar bid Yahoo offered $1 billion to buy Facebook in September 2006 but Zuckerberg turned it down. 'I don’t know what I could do with the money,' Zuckerberg reportedly said. 'I’d just start another social networking site' Reuters Facebook birthday: 15 defining moments for the social network In the money In September 2009, almost five years since the site launched, Facebook turned a profit for the first time Getty Images/iStockphoto Facebook birthday: 15 defining moments for the social network Taking the lead Facebook overtook MySpace in 2010 to become the world’s most popular social network Facebook birthday: 15 defining moments for the social network Taking on the tech giants In 2011, Google launched its own social network that it hoped would knock Facebook from its perch. Despite its initial success, Google+ ultimately failed and will be shut down completely in 2019 Getty Facebook birthday: 15 defining moments for the social network Facebook goes public On 18 May, 2012, Facebook went public. The initial public offering raised $16 billion – the third largest in US history Facebook birthday: 15 defining moments for the social network Gobbling up the competition Facebook acquired Instagram in April 2012 for $1 billion, consolidating its position as the world's leading social network Reuters Facebook birthday: 15 defining moments for the social network One billion users On 4 October, 2012, Zuckerberg announced that Facebook had hit 1 billion users. 'If you’re reading this: thank you for giving me and my little team the honour of serving you,' he wrote in a blog post Getty Images Facebook birthday: 15 defining moments for the social network Expanding its empire In February 2014 Facebook acquired the messaging app WhatsApp for $19.3 billion REUTERS/Dado Ruvic Facebook birthday: 15 defining moments for the social network Two billion users In June 2017, Facebook passed the 2 billion user milestone REUTERS/Dado Ruvic Facebook birthday: 15 defining moments for the social network Privacy scandal On 17 March 2018, news broke that UK firm Cambridge Analytica had harvested data from around 87 million Facebook users for the purpose of political profiling in the build up to the 2016 US presidential elections Shutterstock Facebook birthday: 15 defining moments for the social network Record profits Despite the scandals and subsequent #DeleteFacebook campaign, Facebook posted record profits just before its 15th anniversary, the equivalent of $7.37 from each of its 2.32 billions users iStock/Independent Facebook birthday: 15 defining moments for the social network Unhappy users A study found that people are happier when they don’t use Facebook, adding to mounting evidence surrounding the impact social media has on mental health Rex Features

Mr Zuckerberg and Facebook have recently faced intense political scrutiny for the company’s controversial policy declining to fact-check ads from politicians, something that essentially allows falsehoods.

It has riled Democratic presidential candidates, who have asked for the social media network to remove an ad purchased by Donald Trump’s presidential campaign that they say is false.

Presidential candidate Elizabeth Warren bought a Facebook ad earlier this month in which she joked that the company had endorsed Mr Trump, adding that its policies allow “a candidate to intentionally lie to the American people”.

Sorkin’s entry into the debate marks one of Hollywood’s first broadsides against Facebook on this issue.

In response to Sorkin’s opinion article, Mr Zuckerberg posted the text to a monologue from the 1995 film, citing Sorkin and without additional comment.

“America isn’t easy. America is advanced citizenship. You gotta want it bad, ‘cause it’s gonna put up a fight,” the Facebook founder quoted.

It was a rare move for the chief executive, who has typically refrained from responding to critics on his own platform. Still, he appears to be growing more aggressive when it comes to standing up to the criticism.

Earlier this month, Politico published a story about Mr Zuckerberg meeting with conservative politicians and media. “Meeting new people and hearing from a wide range of viewpoints is part of learning,” Mr Zuckerberg wrote in a Facebook post. “If you haven’t tried it, I suggest you do!”

During an earnings call on Wednesday, he again stood by Facebook’s political ads policy, an hour after rival Twitter said it would ban political ads.

“In a democracy, I don’t think it’s right for private companies to censor politicians or the news,” he said on the call.

Facebook referred to Zuckerberg’s post in response to a request for comment. Attempts to reach Sorkin were not immediately successful.

Sorkin said in the open letter that the CEO did not like The Social Network and called it inaccurate.

“I didn’t push back on your public accusation that the movie was a lie because I’d had my say in the theatres, but you and I both know that the screenplay was vetted to within an inch of its life by a team of studio lawyers with one client and one goal: don’t get sued by Mark Zuckerberg,” he wrote.