It is rare for a dusty old document, fished out of a provincial archive, to become national news. It is even more rare for the people rummaging around the archives to be hard-nosed hacks rather than earnest PhD students.

That is what happened last week after the Daily Mail went digging into the past of Max Mosley, former president of Formula One’s governing body and son of Sir Oswald Mosley, the leader of the fascist “Blackshirts”. After the war, the elder Mosley formed a new far-right party, the Union Movement. Between the late 1940s and the early 70s, it went to the hustings offering the British electorate a ragbag of policies that included a hysterical opposition to immigration by black and brown people from the Commonwealth.

The unearthed campaign leaflet claimed that “coloured immigrants” were being used to lower the living standards of working-class Britons and that they spread tuberculosis, venereal disease and leprosy. Inconveniently, the leaflet carried the name of the party’s election agent, one Max Mosley. As agent, Mosley was legally responsible for the words used.

While old documents being thrust into the centre of the news cycle might be unusual, what isn’t rare today is for past events to shape debates about the present. Many of the biggest news stories of 2017 and 2018 arose from events that took place many years earlier. The subtext to everything from the #MeToo Campaign to angry debates over statues of slave traders and Confederate generals, is the exposure of past misdeeds. The past has returned to shape the present and shame the powerful. Current events have, in a sense, never been less current.

In multiple cases the media strategies deployed by those accused of wrongdoing have fallen back on a “standards of the time” defence. The arguments go along familiar lines: we are urged to remember what it was like “back then”, reminded that it was “a different age”, which can’t be judged by “the standards of today”. The great strength of this defence is that there is some truth to it.

After all, most people in most periods of history tend to follow the accepted views and attitudes of their age, as far as we know. As the views of women, children and poor people were usually of little interest to those in power, how closely they adhered to accepted opinions and moral fashion is more difficult to judge. But for people to make moral choices, for which they might reasonably be judged, they have to have been able to see the alternatives and had access to opposing views. Could they have known differently? That is one of the big questions historians ask themselves. The conclusions reached at the end of such deliberations are almost always complicated, and at the back of the historian’s mind lingers a horrible question – how will future generations view us?

What will our frankly disastrous custodianship of the environment look like to our grandchildren? Who is looking forward to the questions they are going to ask us in our dotage, about air travel or SUVs? And what about modern industrial agriculture – will future generations look back in horror at our annual processing and consumption of literally billions of animals?

History is morally complicated and rarely neat, but the great weakness of the “standards of the time” defence is that it tends to portray as universal views that were controversial at the time, by no means accepted by all. There’s no doubt views like those expressed in the Union Movement leaflet were part of the political debate in 1961, three years before the infamous Smethwick election, in which some Conservatives reportedly used the slogan “If you want a nigger for a neighbour, vote Labour”, a phrase introduced by a far-right party.

According to Harold Macmillan, Winston Churchill thought the 1955 general election should be fought under the slogan “keep Britain white”. On the day the Empire Windrush landed at Tilbury, 11 Labour MPs wrote to their prime minister Clement Attlee warning that “an influx of coloured people domiciled here is likely to impair the harmony, strength and cohesion of our people and social life and cause discord and unhappiness among all concerned”.

Such views, though, were anything but universal. The “standards of the time” trope risks doing a disservice to our ancestors, because to suggest that the people of early 1960s Britain were universally hostile to the arrival of black migrants – or, for that matter, that our Georgian forebears were universally supportive of slavery and the slave trade, or that everyone in the 1890s viewed Africans in the same way that Cecil Rhodes did – is to slander those who rejected such ideas.

Political views are never universally held; they varied as much within periods of the past as they do between them. To suggest otherwise is to use history as a cover for wrongdoing.

Where things get philosophical is on another point Max Mosley made during his car crash interview with the formidable Cathy Newman of Channel 4 News. During that bruising exchange, Mosley stated that the leaflet from 1961 “does not reflect my views today”.

This raises real questions. Do 77-year-olds have a right to denounce their past views? Crimes and abuses have victims and therefore cannot be undone, but views and positions can be repudiated. Almost everyone has youthful opinions that they later rejected. The hand-wringing, bleeding heart liberal in me wants to believe that along the journey from one’s 20s to 70s, minds can be changed and that sometimes the better angels win out.

However, Max Mosley’s more recent support for apartheid makes me suspect that I am being overly optimistic. And as the process by which the crimes of the apartheid regime were uncovered viscerally demonstrated, before there can be reconciliation and reappraisal there has to come truth.

Had it been Max Mosley himself, the author of a hefty autobiography, who had dug out this leaflet from his past then things might look very different. Were he to apologise to West Indian migrants who suffered the effects of the racism the Union Movement stirred up, then the picture might look rosier. And were Mosley more fully prepared to acknowledge that the claims made in the 1961 leaflet were inaccurate and racist, then the idea that a half-century-old leaflet might be the reflection of his twentysomething self rather than the septuagenarian would be easier to swallow.

David Olusoga is a historian and broadcaster whose work includes Civilisations