Peace in Northern Ireland is a delusion. The grim reality since the collapse of the power-sharing assembly in January 2017 is that the historic divisions between unionists and nationalists have deepened still further. More honestly, it is about the division between one extremist branch of unionism and the rest of the people.

Nowhere has this been more obvious than in the differing responses to the prosecution of a former member of the parachute regiment for the murder of two people on Bloody Sunday in Derry in 1972.

Soldier F, as he is designated by the Saville inquiry, he is also facing four charges of attempted murder. The relatives of the 14 people who died at the hands of the British army, along with the rest of the nationalist community, were disappointed that none of the other paratroopers implicated in the shootings were charged.

By contrast, a significant portion of the unionist community were outraged by Soldier F’s prosecution in March this year, and they have attempted to turn his case into some kind of cause célèbre by taking their protests to the streets.

Over the past seven months, banners supporting Soldier F have become a common sight during unionist parades and rallies. Parachute regiment flags fly from lampposts in the Protestant areas of Belfast and Derry. In June, a Soldier F placard was erected near Coleraine railway station. In August, members of a flute band marched through Derry, close to where the atrocity occurred, wearing regimental emblems and Soldier F motifs on their shirt sleeves.

These protests may have been initiated by loyalist extremists but they have received explicit and enthusiastic support from members of the Democratic Unionist party (DUP), on whose support the Conservative government still depend.

After a loyalist parade in Larne on Saturday, at which bandsmen carried a Soldier F banner, the DUP MP Sammy Wilson praised them for “proudly” wearing parachute regiment insignia. He called it “a message” to Westminster to “stop the abuse of the judicial system” by “dragging old men before the courts”.

‘Arlene Foster complained about the way in which police intervened during a provocative Apprentice Boys march in Derry.’ Photograph: James Veysey/REX/Shutterstock

He said: “They have a right to do it, and are absolutely correct in doing so, because they are engaged in a propaganda war that we cannot afford or allow the republicans to win.”

Wilson was echoing a similar statement in August by the DUP’s leader, Arlene Foster, who complained about the way in which police intervened during a provocative Apprentice Boys march in Derry to avoid the possibility of trouble breaking out. She said: “People have a right to support Soldier F. He hasn’t been found guilty [and] he hasn’t gone through due process.”

But nationalists view the Soldier F campaign, particularly the sympathy shown for the parachute regiment, as a grotesque insult that ignores the Saville inquiry’s unequivocal finding after an exhaustive 12-year investigation into Bloody Sunday. It concluded that paratroopers fired on unarmed civilians, killing 13 and injuring 15. A 14th man died four months later of injuries attributed to the incident.

Immediately after Saville issued his report, the then prime minister, David Cameron, issued an apology on behalf of the British government, saying what had happened “was both unjustified and unjustifiable”.

Nationalist politicians have joined with the bereaved in decrying the public demonstrations on behalf of Soldier F. Oliver McMullan, an assembly member and Sinn Féin councillor in Larne, believes the campaign has “caused widespread hurt and trauma” that has “achieved nothing other than bringing further hurt to the families of the victims of Bloody Sunday and souring community relations.”

The hurt has been compounded by the support for the loyalist campaign by former senior British army officers and by the fact that several petitions urging the government to give immunity to troops who served in Northern Ireland have attracted thousands of signatures.

However, the Soldier F issue should not be seen in isolation. It is just one manifestation of the chasm that has widened between the DUP and the other major parties, including the more moderate Ulster Unionist party, ever since the Stormont assembly was collapsed.

The DUP campaigned for Brexit and, despite Northern Ireland voting 55.8% in favour of remain, the party has justified its militant stance by relying on the overall UK leave vote. Its opposition to the backstop, the key to avoiding a hard border with the Republic, has proved to be a stumbling block to Britain’s attempt to negotiate a withdrawal deal.

At the same time, the DUP’s refusal to accept changes to abortion laws, the granting of LGBT rights, such as same-sex marriage, and the guarantee of status for the Irish language have prevented the restoration of the assembly. All of this must also be seen in the context of the DUP’s opposition to the 1998 Good Friday agreement, which ended 30 years of violence in Northern Ireland. No wonder it is so often characterised as “the party of no”.

Much of this, especially the Soldier F protests, will come as a shock to the people of England, Wales and Scotland because the sad truth is that what happens in Northern Ireland tends to stay in Northern Ireland. Although certain flashpoint moments, such as the killing of Lyra McKee in April this year, are covered, too much of the daily grind goes unreported. Newspaper coverage is patchy, and its occasional snapshots fail to convey the real picture.

That negligence means that British voters are kept in ignorance of the reasons for the continuing political impasse. The situation is worsened by the way in which the mainstream media frames the conflict between nationalists and unionists. Its refusal to take sides may suggest it is acting impartially. In fact, it lets the intransigent DUP off the hook.

Imagine, for example, the British tabloid press reaction should banners spring up across London in support of a man charged with murdering two innocent, unarmed people and attempting to murder four more. Would editors avert their gaze? Would they ignore politicians who offered their support to the flag-wavers? Would they overlook the gross insult to the victims’ grieving relatives?

• Roy Greenslade is professor of journalism at City University and a Guardian columnist