And they may have a point. While the vast majority of people in Northern Ireland have shown a willingness to not kill each other, they have been less enthusiastic about the prospect of actually living with each other. Northern Ireland remains very segregated, physically and psychologically. Most people live in neighborhoods that remain overwhelmingly populated by one of the two main traditions: Catholic nationalists, who aspire to unity with the Irish Republic, and Protestant unionists, who want to remain part of the United Kingdom.

It could be the men who murdered Kieran Doherty look around and see that the supposedly new Northern Ireland looks suspiciously like the old one. It could be they see a society still so bitterly divided, still so deeply segregated, that they believe they can exploit historical animosities, that they can capitalize on an almost reflexive tendency among most people in Northern Ireland to view things along narrow sectarian lines, as “us versus them,” an “us” that remains largely defined by a combination of religion and national identity.

The Troubles, as the Irish quaintly call their civil wars, are finished, and Northern Ireland has been held up as a model in conflict resolution, one that has been applied to mediation efforts from the Basque country to Iraq. So why is there still an irredentist rump, still carrying on as if it’s 1972, reducing a complex dispute over power and equality and national allegiance to something as naively simplistic as Brits Out?

Beyond the tragedy for his family, and the 2-year-old girl who will grow up without a father, Kieran Doherty’s abduction and murder seemed hopelessly anachronistic. So, too, did the car bomb that blew up outside a courthouse in Newry, on the other side of Northern Ireland, two days before Doherty was murdered.

His killers, men who call themselves the Real IRA because they think the real IRA sold out by ending its war, issued a statement, saying Doherty was “executed” because he was a drug dealer. In the housing projects of the Brandywell, a neighborhood on Derry’s Bogside that produced its fair share of Irish Republican Army men over the years, there were whispers that Doherty was a tout, an informer, the bane of Irish rebels for centuries. He may have been a pusher or a tout. He may have been neither. But he was certainly a victim of a conflict that was supposed to be over.

For the men who killed Kieran Doherty a few weeks ago, it must have felt like old times. They bound his hands, stripped him of his clothes, and put two bullets in his head. Then they dumped his body on the Braehead Road, outside Derry, near the border, a border separating Northern Ireland and the Irish Republic whose existence has been used to justify murder for the last 90 years.

In the wake of some civil wars, including America’s, the institutionalization of separate but equal is a natural consequence. But, as in the American experience, it is eventually recognized as being a corrosive, negative influence. And the difficulty of breaking down barriers, real and perceived, dogs other divided societies, including those in the former Yugoslavia.

In Northern Ireland, though, there is a lingering acceptance of widespread segregation that belies its role as a model for transforming historically divided societies. In 1971, Reginald Maulding, the British secretary of state for Northern Ireland, cynically suggested the security forces could contain the IRA enough to create “an acceptable level” of violence. The new Northern Ireland seems depressingly willing to countenance an acceptable level of separateness.

In the 12 years that have passed since I lived in Ireland and chronicled the process that led to the Good Friday Agreement, effectively ending the Troubles, I’m always struck upon my annual visits to Northern Ireland by how segregated it remains, despite the near absence of politically motivated violence.

Not only is there an official ethos of separate but equal, but an infrastructure underpinning it. There are three times as many so-called peace lines — elaborate walls separating working-class neighborhoods — than there were at the height of the Troubles, 88 of them at last count.

I walked through Protestant housing projects in North Belfast and noticed many vacant apartments. On the other side of the peace line, the Catholic projects were overcrowded. But there is no attempt to move Catholic families into the vacant apartments because, as they say in Belfast, even the dogs in the street know there’d be riots.

With segregation the status quo, there is an enormous duplication of public services, such as schools, community centers, and health clinics. The Alliance Party, the only major political party that draws substantial numbers from both sides of the divide, estimates that duplication of public services costs more than $1 billion a year, this in a place the size of Connecticut with a population of less than 2 million.

But it’s more than money that Northern Ireland is losing. It is losing the very kind of people that might change things. Some are voting with their feet, others simply not voting at all. Voting participation, which surged in the optimism following the Good Friday Agreement, has slumped. The brain drain, which saw educated young people head to England and everywhere else, slowed after everything looked possible in 1998. But it has picked up again, as a new generation that grew up without widespread violence concludes that peace is nice but not everything. So much creativity, energy, and productivity, lost across the Irish Sea.