Finally: there’s a debate about media bias. It’s becoming an unfortunate missed opportunity, though, because so far it’s only focusing on the leftwing blogs that have emerged in the past couple of years. Whatever the failings of, say, the Canary, it only gained traction because there is a substantial body of opinion in Britain which feels marginalised, unheard, and attacked by the broader media.

The reason for that is this. Britain’s press is not an impartial disseminator of news and information. It is, by and large, a highly sophisticated and aggressive form of political campaigning and lobbying. It uses its extensive muscle to defend our current economic order which, after all, directly benefits the rich moguls who own almost the entire British press. Whether it’s the Sun, the Telegraph, the Times, the Daily Mail or the Daily Express, that means promoting the partisan interests of the Conservative party. The press has been instrumental in upholding the political consensus established by Thatcherism: deregulation, privatisation, low taxes on the rich and weak trade unions. It has traditionally defined what is politically acceptable and palatable in Britain, and ignored, demonised and humiliated individuals and movements which challenge this consensus.

The press abounds with writers who are just as opinionated as me – but their opinions go in the news section

Rather than challenging powerful interests, the press is more interested in punching down, disseminating myths and outright lies in the process: from Hillsborough to immigrants to benefit claimants. Polling shows widespread acceptance of myths on everything from the true levels of benefit fraud and teenage pregnancies to how many immigrants there actually are in Britain, and media coverage plays a critical role in spreading these dangerous misconceptions. In the first two years of the Tory-Liberal Democrat government, a coalition of disability charities reported a surge in hate crimes against disabled people, partly because of inflammatory media coverage.

The distinction between “news” and “opinion” throughout much of the British press is blurred. I write opinion, and it goes in the opinion section of this newspaper. The press abounds with writers who are just as opinionated as me, but their opinions go in the news section. I am a political activist, but so are they: they, too, use their “news” writing as a means to advance political aims and causes, even if they pretend otherwise.

Then there’s the commentariat. The explosion in opinion is problematic. It has all too often supplanted investigative journalism, which is expensive and takes up a lot of time, often without guaranteed results. The collapse in newspaper revenue has led to cuts to invaluable reporting and its replacement by opinion, which is cheaper, can be turned around quickly and can garner a lot of revenue-generating clicks.

Pundits do play, at least in theory, an important role in democracy. The problem is that the British commentariat is by and large a cartel: its members are mostly there because of their views, their backgrounds, and – to varying degrees – their connections. Only one in five leading British print journalists were educated at comprehensive schools, in stark contrast to about 90% of the population. Our backgrounds inevitably play an important role in forming our worldviews, determining our priorities and creating our blind spots.

The spectrum of opinion represented in the commentariat is limited indeed. There is a broad consensus on economic issues – a big role for the market, a limited role for government – and contempt for ideas that challenge this consensus. As a recent study found, there is overwhelming support for public ownership of utilities: you will struggle to find anything other than derision for such ideas in almost the entire commentariat. Their view is this: repeating nostrums – often eloquently – that defend the status quo is nuanced, thoughtful, balanced. The isolated voices in the commentariat who depart from this consensus are predictable, infantile, dogmatic.

Despite the dramatic collapse of much of their worldview – from the financial collapse to the 2017 general election to disastrous foreign interventions from Iraq to Libya – their sense of superiority remains a defining hallmark. The Financial Times’s Janan Ganesh once described Jeremy Corbyn supporters, for instance, as “thick as pigshit”. There is no evidence that he or his colleagues have conceded that any of the pillars of their worldview are wrong. The opposite: the onward march of political wrongness, as they would see it, simply vindicates their rightness. The popular mood is a mass delusion and a departure from reason.

The debate on broadcast media, such as it is, has focused on the BBC’s Laura Kuenssberg. There is a troubling element of sexism in how Kuenssberg has been singled out, indeed targeted, for alleged rightwing bias. There are prominent male broadcast journalists who have outright partisan backgrounds (some used to be prominent Tory activists; the BBC’s Andrew Neil is a climate change sceptic and chairs the media owners of the rightwing Spectator magazine), and they don’t receive the same level of bile. Her treatment is wrong. It also represents a failure on the part of her detractors to understand that the problem is systemic, rather than down to the shortcomings of individual journalists. The priorities of broadcast news are in large part determined those of the rightwing press: their headlines and angles often frame debate on TV and radio each day.

As a 2013 Cardiff University study found, the BBC is far more likely to interview business representatives than trade union voices (in 2012 the ratio was 19 to one). During the financial collapse, the study found, BBC interviews were dominated by voices from the City. They were treated as witnesses, as informed commentators, rather than being interrogated for their role. Imagine, during the winter of discontent, trade union leaders appearing on the BBC as expert voices rather than being held to account for “chaos”? The problem with broadcast news coverage is that it treats the status quo as “neutrality”: the voices that departed from the consensus are to be checked for bias.

A media so weighted in favour of the status quo makes progressive, campaigning journalism a necessity. Much of modern journalism exists – often aggressively so – to defend the way society is currently structured. And yet when what remains a small, marginalised counterweight emerges, to make the case for a different form of society, it is portrayed as a dangerous threat to journalism.

Yes, some leftwing blogs exhibit problematic approaches to journalism: but then there’s the likes of Novara which is at the cutting edge of new left ideas. But if the mainstream media catered more for views which challenge the existing order of things, a vacuum would not have been left to be filled. In this year’s election, four out of 10 voters just opted for a Labour party offering an unapologetically socialist platform. It is a travesty that the ideas represented by that manifesto remain fringe opinion in the British press. Our media has a straightforward choice. Cater for the growing demand for dissenting views – or be challenged by new media outlets that do.

• Owen Jones is a Guardian columnist