When the Hillsborough Independent Panel Report was published last year, restating the police's responsibility for the disaster and the staggering lengths the force went to cover it up, former Labour Home Secretary Jack Straw was quick to blame the Conservative government of the time. "The Thatcher government, because they needed the police to be a partisan force, particularly for the miners strike and other industrial troubles, created a culture of impunity in the police service,' he told BBC Radio 4. "They really were immune from outside influences and they thought they could rule the roost and that is what we absolutely saw in south Yorkshire."

The underlying message of Straw's comments resided in his use of the past tense. If nasty Thatcher had used the police as a political tool back in the bad old days, thankfully now things have moved on. There's been welcome progress. Yes, there might still be the odd 'bad apple' – remember poor Andrew Mitchell! - but for the most part the police have returned to their default position as the heroic thin blue line, neutrally protecting the good guys from the baddies.

This assumption - that, despite the odd mishap, the police are trying their best in a tough job – is driven home on a daily basis by reams of police TV dramas, movie detectives and 'real life' documentaries. Sure, they might be forced to play by their own rules sometimes, but ultimately, their only agenda is the upholding of 'decent, hardworking' society. The strength of this torrent of 'ideology-by-ITV' is perhaps one reason why, even when presented with story after story of police aggression, racism, corruption and violence, many people's reaction – or at least that of white, middle-class people - remains one of shock, rather than expecting nothing less. Perhaps it is also explains why when the Guardian published a video last week clearly showing a policeman punching a student in the face, the newspaper chose to put quotation marks around the word 'punch'.

Jack Straw being wrong is hardly a rare occurrence, but if further confirmation was needed, then events last week certainly provided it. Wednesday night saw the violent eviction of a student occupation at Senate House, with the aforementioned video footage showing police punching and throwing students to the floor circulating widely. On Thursday, the final witness took to the stand at the inquiry into the death of Mark Duggan, whose shooting by police in August 2011 sparked four days of anti-police rioting. That afternoon, students protesting against the previous night's violence were again attacked by riot police, with one student being knocked down so hard he left a pool of blood on the pavement. The next day the United Friends and Family Campaign, led by families of people who have died after contact with the police, held a picket outside the Crown Prosecution Service HQ, demanding that police officers responsible for deaths face criminal charges.

As the Guardian's reporting shows, all this has still not been enough to shift the default image of the police from one of the benevolent 'bobby on the beat' to 'corrupt, violent thug'. But cracks in the ideological edifice are beginning to show. Black and ethnic minority communities have long known about police violence, repression and racism of course – as have residents of former mining towns, the Hillsborough families and their supporters, Northern Irish Catholics, and traveller communities. But the skull-cracking force used to put down the 2010 student protests, and the routinely aggressive policing of virtually any form of protest since – from anti-fracking to anti-fascism – has begun to spread counternarratives about the police's role and behaviour more widely than ever before. Increasingly, the most explosive flashpoints - the sharpest antagonisms - in this era of fierce austerity and collapsing wages, are taking the form of explicitly anti-police protests or riots. Equally, from the opposite side of the equation, police repression is now used as the first rather than last resort even when it comes to dealing with protests about corporate tax avoidance or cleaners' working conditions.

In 'Policing The Crisis', Stuart Hall et al argue that the roots of this kind of policing can be found in the economic crisis of the late 1960s. The post-war social democratic consensus had been characterised by direct state intervention in class relations, with both business leaders and trade unions negotiating directly with the government. In this way, economic class struggle was increasingly drawn onto the terrain of the state itself. But this delicate balancing act was dependent upon continued growth and productivity. When the crisis hit, it therefore threatened not only the economy, but the legitimacy of the state as a whole as well as the 'social order' of the capitalist society established under it.

Because there became no difference between 'social order', the 'national interest' and a 'functioning capitalist economy', every manifestation of social or economic antagonism – from trade unions to punk – was instantly transformed into a threat to society as a whole. There could be no recognition that different groups of people within that society had conflicting interests. There was only one recognised interest: the recovery and strengthening of capitalism. You were either on the side of 'order' and 'authority', or else you were the 'enemy within' threatening to unleash 'chaos' – and thus a legitimate target for a militarised police force and surveillance state.

This aggressive rhetoric was closely related to the particular way in which a crisis-hit capitalism was, for a time, put back on its feet. The transformation from a labour-intensive Fordist manufacturing economy to a capital-intensive post-Fordist economy of services, finance and rent-seeking required the throwing off of large numbers of jobs and workers, a process that was intensified by the development of labour-saving technologies within industrial production. While some of the labour no longer required in manufacturing could be reintegrated into the new lines of capital, the remainder was doomed to a lifetime of falling in and out of precarious, temporary, low paid work, or faced being locked out of the labour market altogether.

The recovery of capitalist society was therefore dependent on the exclusion of a substantial number of people who were becoming surplus to capital's requirements. And it was the police's crucial job to ensure that the line of exclusion was not breached, to make sure that those on the outside of the system were not able to get back in – for fear they'd bring the newly-restored 'social order' down with them. For most of the 1980s and 1990s, this excluded group was predominantly made up of black and other ethnic minority people, the residents of former industrial towns left to rot by capital fleeing the scene of a crime, or ASBO-ed and NEET-ed young people demonised in the media. It is these groups who have borne the brunt of the fierce police and penal system needed to keep the system going, whether that is through incarceration, violence, stop-and-search or benefit sanctions.

But the crisis of 2008 destroyed the capitalist salvage job cobbled together in the late 1970s and demanded a new bout of exclusions to fix it. This time it's not just the remnants of old labour, the poorest and the non-white who are being shut out – it's the next generation of middle-class workers too. Young people today are being excluded from the labour market in unprecedented numbers, which is why, as Aaron Bastani correctly notes, the student protesters of last week are making connections between their own prospects and those of outsourced cleaners and the 2011 rioters. Quite simply, capital cannot survive unless it pushes the wages of vast swathes of people to as low a level as possible, or even better, turns them into debt peons or forced labourers. If this increasingly excluded population force their way back into contention, the fragility of a re-reconstructed capitalism as a whole is put at stake. With no possibility of assuaging a surplus population - trapped outside of the capital-labour relation - through economic means, repression is revealed as the only option left to the capitalist state.

In a sense, capital's fragility and a ramped up repression are two sides of the same coin. Economic growth is so desperately sought that even that of soaring house prices and consumer debt – the very same 'growth' which kickstarted the crisis in the first place - is celebrated manically. Therefore anything which hinders that 'growth' in any way, from stopping fracking drills to squatting in empty houses or shutting down a shop for an afternoon, is regarded as an attack on the whole of capitalist society. Because, in a way, it is. For all the pain and suffering that it is currently inflicting on the working and non-working class around the world, capital is actually in a historically weak position. It is running out of options. It has to control the entirety of society, regardless of the repression involved, or else it collapses.

There is therefore a crucial difference between the protesters demanding pensions and sick pay and the rioters - in that the rioters have realised that there is no point in even asking capital for anything anymore. Under current conditions it has nothing to give them, not even exploitation. But the logic is still the same: excluded people raging at the edges of a capital-labour relation that is becoming ever more abstract and distant. In both cases, the police start to become the only visible indication of the antagonism of that relation which remains. The danger is that because the police are virtually the only tangible target left, the only place from which to get a foothold in the class struggle, that they are turned into the cause rather than a symptom of the situation. As an essay from the SIC journal puts it neatly: 'in revealing the cops as an enemy in itself, what becomes obscured is the fact that they are only the bourgeoisie in fighting position.'