These have been a dreadful couple of years for the left. The Coalition was succeeded by the first majority Conservative Government in over 20 years, the Labour Party continues to tank in the polls under the incapable but persistent Corbyn, the EU referendum went against them thanks in no small part to millions of traditional Labour voters, and now Trump has not only defeated Clinton but appears to have attracted more than a few former Democrats in doing so.

It’s easy in retrospect to nod and say it was all inevitable, but it’s worth remembering that it wasn’t supposed to be like this.

Back when the financial crisis struck, we were told that the centre right was doomed by association with the failures of capitalism. The left would win the arguments and scoop up the support of aggrieved voters. At the same time, generational change was supposedly working its magic – the high water mark for Euroscepticism was 1975, opposition to Brussels would dwindle as older voters died out, the woeful Tory polling numbers among young people would march up the age chart, Thatcher’s children would spend their lives in rebellion against Toryism and so on. The Tories, the Eurosceptics, the Republicans and anyone else deemed distasteful would never, ever win again.

These arguments were evidently flawed. Rather than voters reacting to an economic squeeze by turning to the magic money tree, they hardened their fiscal attitudes with the same resolve that they took to their own finances. Fiscal conservatism became more popular, not less – it turned out that people might tolerate costly green policies and a wasteful welfare system when they had money to spare, but were less keen on them when their own budgets became tight.

The demographic assumptions also turned out to be a fantasy. We might call this the Peter Pan Fallacy – the mistaken idea that young people will never change as they grow older, but instead will hold tight to all the left-wing mantras of the student union even when they become businesspeople, taxpayers and parents.

It’s understandable why the idea appeals – it’s easier to blame the old for being stubborn than to acknowledge you might have failed to convince people, and more comfortable to view eventual victory as a demographic inevitability than to face the changes and hard work that might be required to actually win in future. But it has proved to be a dangerous dead end for the left, lulling them into false confidence about their future and leading them to indulge in disastrous expressions of contempt for voters whose support they need.

This error is observable from outside their movement, but within it it seems to still be treated as heresy. Those who suggest that maybe deriding voters as ignorant, bigoted bedblockers is counter-productive are howled at as neoliberals, Blairites and traitors. The flow of hatred and blame towards the electorate continues and intensifies – it could be seen in the student riots, in the spitting thugs outside the Conservative Party Conference last year, in the collective meltdown on Facebook after the referendum and in the rioting and fury we’ve seen this week.

No-one expects happiness in defeat. None of us feel it when we experience defeat ourselves. But it is reasonable to ask that people accept outcomes they dislike under rules they accept when they win and that they don’t take defeat as license to lash out at those they blame for being to ignorant or unpleasant to recognise their moral superiority. Not only is it harmful to our democracy for one side to try to undermine its legitimacy when things don’t go their way, but the feedback loop of left-wing failure, left-wing contempt for voters and then more left-wing failure only serves to produce ever more ineffective opposition. To borrow Boris Johnson’s term, the “whinge-o-rama” brings no benefit and only does damage.

To better serve its own ideals, and to stop harming the cohesion of society, the left needs to face a very uncomfortable fact: all the things that they rage against have only been possible because of their own actions. Some of those – like the Tory majority and leaving the EU – I’m glad about. We were lucky in our opponents and the nation will benefit as a result of their failings. Others – namely the election of a Putin sympathiser and NATO opponent to the White House – worry me. But in each circumstance, those who are most angry have only their own mistakes to blame. The depth of their anger hints that they are dimly aware of this already in the deepest regions of their hearts.

The temptation to scream rather than think currently appears too great, however. The echo chambers of social media reinforce that temptation, as the outraged rack up retweets and likes from people who already agree with them, without considering the impact on those they actually need to persuade in order to move things in their direction in future. The result will simply be more of the same; people tend not to forget being characterised as idiots and racists, even if the speaker comes to regret the words shortly after saying them. Just as harmful is that words can be rinsed of meaning over time – smear reasonable people as extremists simply for disagreeing with you, and you will soon find that no-one listens to your warnings when real extremists come along.

Two roads diverged in a wood, as Robert Frost wrote. The one most travelled at the moment – the path of fury at voters, denial of democratic verdicts and questioning democracy itself – is inviting and familiar, but only leads the left deeper and deeper into a wasteland. The other – which the path of tough reflection and self-scrutiny – might be rougher for the first few miles, but ultimately offers a far better view and a viable future. Their error can be corrected; they strayed towards the former in the 1980s but dragged themselves onto the latter eventually. Let us hope they manage to repeat the feat.