Early in the morning, the sky still dark behind him, a man climbs on to a tube train in one of the less wealthy patches of east London and prepares to make a stand. After weeks of climate protests across the capital, its commuters have arguably grown used to navigating scenes such as this. But what happens next, in the footage shot by an ITV journalist and spread virally across social media, is disturbing on many levels.

Passengers on the packed platform, sensing they’re now going nowhere, react furiously. A voice can be heard shouting: “I need to get to work! I have to feed my kids!” One man, boosted by the crowd, grabs for the protester’s legs; the protester appears to kick out towards his head. The protester is white. The man below him is black. The protester is quickly dragged down into a surging crowd, rescued only by the intervention of other passengers and a London Underground worker. And suddenly, we are a long way from cheering scenes of giant pink octopuses being escorted down Whitehall, or grey-haired pensioners submitting courteously to arrest.

Halting the climate crisis is obviously urgent – but for most people, being able to pay the rent is a different degree of urgent

Extinction Rebellion in particular, and climate warriors more broadly, have long been accused of being too middle-class, too white, or otherwise insufficiently conscious of their relative privilege, when blocking roads down which other people are struggling to get to work. That criticism was more easily shrugged off while the protests were mainly confined to the streets around parliament, although appeals for donations of “ready-to-eat vegan food” and warm clothes for those voluntarily camping out did feel somewhat insensitive in a city with so many rough sleepers.

But the ugly standoff at Canning Town station is a wake-up call, illustrating the risks to a fledgling movement that has so far enjoyed huge reserves of goodwill from the millions broadly sympathetic to its cause. It should go without saying that mob violence is never justified; that anger and frustration should not be expressed with fists. But if you’re on a zero-hours contract, knowing that being even a few minutes late means your shift will be cancelled today, then it doesn’t really matter what political point is being made by the guy stopping your train leaving or your bus getting across the bridge. What matters is that you’re scared.

The same is true for anyone who knows their boss could replace them tomorrow on a whim, or whose life is already stretched so thin it can’t take much disruption, or who sees their livelihood disappearing beneath their feet. Halting the climate crisis is obviously urgent – but for most people, being able to pay the rent is a different degree of urgent, and failing to acknowledge that is arguably the single biggest threat to this campaign succeeding.

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Targeting public transport is an oddly self-defeating thing for environmentalists to do, and this particular action has clearly dismayed some within Extinction Rebellion. As a loosely networked grassroots movement, it can’t always control what supporters choose to do, but the results of an internal poll of members, shared with the Guardian, showed 72% opposed action on London’s underground network. But the problem here isn’t just tactics. If protesters started blockading coal-fired power plants or petrol stations or car factories, it might seem more logical than glueing themselves to electric trains, but they could trigger a similarly angry backlash from workers sensing their livelihood was under threat.

The deeper problem is a reluctance to confront the painful human consequences of Extinction Rebellion’s uncompromising demand that Britain achieve net-zero emissions by 2025 – not 2050 for the UK overall and 2045 for Scotland as the government advisory body the Committee on Climate Change (CCC) report recommended – and the thorny questions raised about public consent. The climate crisis frightens me as much as it should frighten anyone, and Extinction Rebellion deserves huge credit for popularising the argument. But alarm bells ring when I see one of their spokespeople blithely telling the TV cameras that it doesn’t matter if their demands are practical; all that matters is that they’re met.

The thing that distinguishes Extinction Rebellion from more established green movements is that it wasn’t founded to achieve change by winning over public opinion en masse, and thus prodding governments to act. Instead it’s founded on the idea that gradualism doesn’t work, while a critical mass willing to make life difficult for others can bring down even mighty systems.

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Although Extinction Rebellion supporters will differ over how far to push it, the original model is more of a revolutionary than a democratic one. And the clashes at Canning Town feel like an early warning of what can happen when the idea of public consent is brushed aside by people convinced they don’t have time for all that. What we need now aren’t smarter revolutionaries, but elected politicians capable of translating all this raw passion into something that works for everyone.

A Conservative government that barely even acknowledged climate chaos in this week’s Queen’s speech has obviously failed to rise to the moment. So now it’s for Labour to somehow bridge the yawning gap between party conference delegates who voted for a 2030 target last month, and the practical realities of securing what shadow secretary of state for business, energy and industrial strategy Rebecca Long-Bailey calls a “just transition” (a phrase also used by the CCC) in which the vulnerable are protected from potentially seismic economic and social change.

The very word “practical” is a red flag for some, seen as code for selling out. But any political movement refusing to engage with the bread-and-butter concerns of low-paid, marginalised or justifiably anxious people – which is what “practical” means here – cannot call itself progressive. That the poorest will suffer most from global heating is no excuse for trampling them in the rush to do something about it.

• Gaby Hinsliff is a Guardian columnist

• This article was amended on 18 October 2019 because an earlier version referred to Rebecca Long-Bailey as shadow environment secretary, rather than shadow secretary of state for business, energy and industrial strategy. This has been corrected.