Jeremy Corbyn did an event in Stoke last night, and a reporter interviewed some of the 400 or so supporters who had turned out to hear him. Among other things, Lewis Goodall of Sky News sought their views on “wreathgate”, the ongoing row about the ceremony Corbyn attended in Tunis in 2014. “Everyone we spoke to agreed,” Goodall wrote afterwards. “Corbyn is being smeared, Labour does not have a problem with antisemitism and that the whole thing is largely concocted by the media and Tories.”

One of the more useful phrases of our time is “tribal epistemology”, the notion that what people know is increasingly linked to the group they identify with. The wreath row has been a case in point. There is no single, agreed set of facts on which the various sides hold different opinions. Instead, among those most heatedly involved, the facts or evidence people see and don’t see depend on their tribal or factional affiliation.

Quick Guide Jeremy Corbyn wreath-laying Show What is the controversy about? Jeremy Corbyn has said that he was present but not involved at a wreath-laying for people behind the group that carried out the Munich Olympics massacre. The row centres on a wreath-laying event in Tunisia for two separate groups, both the victims of a 1985 Israeli airstrike in Tunis and for the Palestinian leaders linked to the Black September terror group who killed Israeli athletes. There are memorials to the victims of the 1985 bombing and a four graves for leading figures from the Palestinian Liberation Organisation, thought to have been behind the Black September group, in different parts of the cemetery. What was Jeremy Corbyn doing in Tunisia? Corbyn was attending a conference in Tunisia called the International Conference on Monitoring the Palestinian Political and Legal Situation in the Light of Israeli Aggression. In an article for the Morning Star in 2014, shortly after his visit, Corbyn said he was present for a ceremony honouring the 1985 victims and “others killed by Mossad agents in Paris in 1991”. The Palestine Liberation Organisation’s intelligence chief Atef Bseiso – who has been accused of involvement in the Munich Olympics massacre – was killed in Paris in 1992, purportedly by Mossad. No-one was killed in Paris in 1991, so Corbyn may just have got the wrong date. What do his critics say? On Saturday, the Daily Mail published pictures of Corbyn holding a wreath at the Palestinian Martyrs’ Cemetery in Tunisia. The paper said that its own visit to the cemetery had shown that the memorial for the victims of the 1985 bombing was 15 yards away from the spot where Corbyn was pictured holding a wreath. The story claims the pictures were taken in front of a plaque honouring the founder of the Black September and yards from the grave of Bseiso. What does Corbyn say? Corbyn said that “a wreath was indeed laid” for “some of those who were killed in Paris in 1992” and added, in response to a question: “I was present at that wreath-laying, I don’t think I was actually involved in it.” He added: “I was there because I wanted to see a fitting memorial to everyone who has died in every terrorist incident everywhere." Labour has said that Corbyn had already made clear he was paying his respects to the victims of a 1985 Israeli air strike on Palestinian Liberation Organisation offices in Tunis. But Corbyn’s remarks indicate he was at least aware of another wreath-laying at the memorial event.

Which is how a set of photographs from a Tunis cemetery has become the object of such controversy. Neutrals are probably either confused by the whole business and tune out, or they tend towards the view of that crowd in Stoke: that the media have falsely trashed Corbyn in the past – witness the baseless Czech spy accusation – and therefore are not to be taken too seriously now.

For those reasons, Corbyn and Labour will surely ride out this current storm. Nevertheless, rows like this one are not good for the party: they take up time and energy that might otherwise be devoted to opposing the government or advancing Labour’s own programme. How then should Labour deal with this argument and others like it which, if the past is any guide, are likely to keep on coming?

On the Tunis episode, there are three options. The first is to say that everything that happened, every wreath that was laid, was solely in honour of those killed in the 1985 Israeli bombing of PLO headquarters in Tunis. That was the line taken by the pro-Corbyn MP Chris Williamson as he toured BBC studios on Tuesday, and enthusiastically echoed by Corbyn supporters online. Its great strength is that deploring the 1985 bombing is not controversial: even Margaret Thatcher did it.

But there are two problems with the “1985-only” line. For one thing, the photographs clearly show two distinct wreath-laying moments: one at the 1985 memorial, with Jeremy Corbyn hovering at the back, and another at a visibly different location, by the graves of senior PLO leaders reputedly involved in the 1970s with the Black September faction, which organised the massacre and torture of Israeli Olympic athletes in Munich in 1972. The men buried there had no connection with 1985, and it’s in that location that Corbyn is pictured holding a wreath.

What’s more, Corbyn himself explicitly wrote, in the Morning Star after the Tunis trip, that 1985 was not the sole focus of the ceremonies: “Wreaths were laid at the graves of those who died on that day and on the graves of others killed by Mossad agents in Paris in 1991.” So the photographs and Corbyn’s own words make the 1985-only line unsustainable.

The second approach available to Corbyn would be to say that he has long been a devoted supporter of the Palestinians and on that day in 2014 he was not going to get too hung up on the exact details of this plaque or that grave, which were anyway opaque to him as a non-speaker of Arabic: what mattered was standing in solidarity with his Palestinian friends. But perhaps he worries that would sound insufficiently discerning for a would-be prime minister.

The third option would be to say: “Yes, as the photographs show, I did lay a wreath at the graves of Salah Khalaf, known as Abu Iyad, along with Hayel Abdel-Hamid and Fakhri al Omari. I knew exactly who they were and I make no apology for that.” The argument the Labour leader could make would be that perhaps those men were leaders of the group behind the murderous Munich attack, but they changed course: Khalaf became one of the prime proponents of the PLO’s shift away from violence and towards diplomacy. Corbyn could say that it was precisely that journey that he was honouring that day in Tunis.

The trouble is, if that had indeed been Corbyn’s motivation he would surely have mentioned it in that Morning Star article or since. Instead he has left the impression that he is a bit vague about who these men were. He wrote that they were killed in Paris, when in fact it was Tunis. He said they were killed by Mossad agents, when in fact they were killed by a rival Palestinian faction. (It’s possible Corbyn was confusing those three with a fourth man, Atef Bsesio, also allegedly linked to Munich and also buried in that same cemetery: he was reportedly killed by Mossad agents in Paris – though that was in 1992, not 1991.)

The point is, there is a way to deal with these questions which, given Corbyn’s record of activism, will keep coming. It will require precision and candour, rather than I-didn’t-inhale formulations such as “I was present but not involved”, especially when the pictures say otherwise.

Chiefly, it will mean honestly admitting that when he attended events like this one – and this goes for his history in Northern Ireland too – he was not there as some neutral peace broker, as he now suggests, but as a vocal supporter of one side against the other. He was not an intermediary in either Israel/Palestine or Northern Ireland: if he had been, he would have been scrupulous about meeting all sides, which he never did, and expressing either no solidarity with any side or plenty with all of them, which was also not his way.

Instead, in Israel/Palestine his position was not that of a healing conciliator of two warring peoples, but rather “to eradicate Zionism”, to cite the stated goal of the Labour Movement Campaign for Palestine of which he was a sponsor. In Northern Ireland, he was for republicanism and against unionism, taking part for example in a 1987 ceremony to honour not all victims of terrorism, but eight IRA gunmen killed by the SAS. As he put it at the time: “I’m happy to commemorate all those who died fighting for an independent Ireland.”

In these conflicts, Corbyn did not sit on the fence or act as some even-handed negotiator. He chose sides. That’s what makes him who he is; it’s what many people admire about him. To his most loyal supporters he can perhaps pretend that he spent decades as some kind of unofficial UN peace envoy. But for everyone else, he needs to have an honest, precise reckoning with his past. Otherwise, what happened this week will keep happening.

• Jonathan Freedland is a Guardian columnist