When Mark Zuckerberg appeared before the US Congress this spring he insisted he was not running a media company. But it is getting easier to say why he does. Facebook, the site Mr Zuckerberg founded almost 15 years ago, hosts and produces content. It sells advertising against content. It employs thousands of moderators who help patrol the content it “surfaces”. Two months after he gave his testimony Facebook, without irony, announced plans to launch news shows on its video portal. Its database of privately shared information and personal connections has been used to destabilise democracy. Mr Zuckerberg ought to be held accountable for running a media company.

The billionaire will resist this. His no-show at the House of Commons this week was a snub to representatives from nine parliaments. It is part of a deliberate defensive strategy to delay, deny and deflect criticism. This will only make the regulatory backlash bigger. History shows that political power can be brutally enforced over an influential private enterprise when it has compromised morality for the sake for profit. Facebook might be able to brush off allegations it is too addictive. But it cannot dismiss so easily the charge that it is bad for democracy. The company is long overdue a regulatory reckoning.

Facebook did too little to stop Russian interference in the US election in 2016. The company was fined in the UK for breaking the law after it emerged it had shared the personal data of almost 90 million users with outside third parties without permission. Last week, after a flurry of denials, Facebook admitted hiring lobbyists to disparage critics. A decade ago Rupert Murdoch fought to discredit the phone-hacking scandal that enveloped News International. In the end, many were convicted, Mr Murdoch closed down the News of the World and the media mogul appeared before MPs in “the most humble day” of his life. He revealed an organisation in ethical and organisational turmoil. Mr Murdoch had lost in the court of public opinion and the verdict handed down diminished his legacy.

Undue dominance of the media always poses a potential threat. In Britain, Facebook has become third only to the BBC and ITV as a source of news despite spreading prejudice and falsehood. The media watchdog Ofcom is right to say social media must be regulated. Around the world, Facebook has been used to disrupt elections, spread viral propaganda and promote deadly campaigns of hate. When an investigative journalist from the Philippines confronted Mr Zuckerberg about Facebook being the “fertiliser” of democratic collapse, noting 97% of her country were on it, the billionaire replied: “Oh well. What are the other 3% doing?” Mr Zuckerberg is a menace to society because he disputes public accountability for what his company does, and is loth to consider society’s interests as well as his own.

There is strong public interest in having Facebook regulated as a media company. Lawmakers must consider ways of curbing how it uses data to target advertisements and what information it makes available to third parties. Like any other media company, it ought to face strict advertising regulations and tough transparency requirements in elections. Given its dominance in digital advertising, Facebook, which also runs Instagram and WhatsApp, is a candidate to be broken up. Like many tech firms, Facebook promotes the idea its commercial interest is intertwined with the public interest. That has led to an abuse of power and a threat to democracy, which lawmakers have a duty to find the best protections against.

• This article was amended on 29 November 2018. An earlier version said that “Facebook has become second only to the BBC as a source of news”. That should have said third only to the BBC and ITV.