Was that it? Last night’s Dispatches on Channel 4 was trailed as a damning exposé of Momentum, the pro-Labour grassroots movement widely demonised by the media as a sinister rabble of Trotskyist infiltrators. Instead, viewers were treated to a baffling boreathon, a programme that veered more towards pernickety than scandalous. Rather than being led by revolutionary disciples of Leon Trotsky, most of Momentum’s leaders aren’t really ideologues of any sort: two are former primary school teachers with a passion for social justice.

To fuel a “reds under the beds who want to collectivise your children” narrative, the documentary predictably bigged up the Alliance for Workers Liberty, a Trotskyist group with 100 members (Momentum has over 17,000), many of whom were in the Labour party when Tony Blair was leader. If it was the searing indictment that had been trailed, Tory MPs would have been all over it. Instead, Zac Goldsmith – the Tory MP who disgraced himself with his racist London mayoral campaign – described it as “weak. It will only reinforce the view that the establishment wants to trash Corbyn. Suspect it’ll have the opposite effect.”

#Dispatches was weak. It will only reinforce the view that the establishment wants to trash Corbyn. Suspect it'ill have the opposite effect — Zac Goldsmith (@ZacGoldsmith) September 19, 2016

Whingeing about media bias is one thing, but how do progressive movements deal with it? Britain’s broadcasters largely follow the agenda set by the press, and Britain’s press is not only mostly run by a tiny group of wealthy rightwing moguls, its aggression also has few parallels in Europe. Take the Brexit vote. Leaders of the leave campaign were keen to present themselves as at the head of an anti-establishment rebellion. And yet a study by the Reuters Institute for the Study of Journalism found that – when circulation was taken into account – 48% of articles in the UK press during the referendum were pro-leave, compared to just 22% that supported remain. In other words, Britain’s press decisively threw their weight behind the leave cause.

A defeatist attitude – and a condescending one, too – says that the media programme people with what to think, reducing the electorate to Murdoch-brainwashed zombies. But a clever approach can neutralise media hostility. Take Sadiq Khan: he was subjected to one of the most vicious political campaigns in postwar Britain, portrayed by the press – including London’s dominant newspaper, the Evening Standard – as the pawn of Islamist fundamentalist extremists. He could have bellowed his frustration every single day, and would have been more than entitled to do so. But he didn’t. He focused on a positive, optimistic message, and not only won the election – he had glowing personal ratings, too.

Momentum, too, presented a masterclass last weekend in dealing with hostile media. Rather than taking aggressive swipes at the media, it framed a response to Dispatches before it was even aired. It projected disappointment rather than fury; it gave a platform to Momentum activists who contrasted sharply with the media portrayal; it was witty; and it showcased what it actually did, using the attack as an opportunity to get its own message across. And there is a lesson there. The left is bitterly accustomed to living with almost farcically hostile media in a country where the press is as much a sophisticated political lobbyist as a means of information. A natural response is to become grouchy, to shake fists angrily, or simply boycott the media altogether. It’s an approach that fires up some of the most dedicated leftwing activists, but it’s a strategic mistake. And both Khan and Momentum show the left can rebut media hostility – and even thrive.