What turns somebody into a so-called paedophile hunter? Vein-popping levels of rage seems to be a big factor going by the shocking evidence gathered by BBC reporter Kevin Magee, not to mention a gargantuan, out-of-control ego.
West Belfast man George Keenan, door-stepped by Magee, truly was a sight to behold. Alternately ranting, hectoring, and using about four different bizarre accents in quick succession, he seemed so consumed with self-righteous anger that it looked as if he might actually burst.
After a hostile confrontation in which Magee was surrounded, harangued and pursued by Keenan and a gang of his fellow vigilantes, Keenan admitted that the objective was to "inject fear".
Magee said that in all his many years as a journalist, he had never experienced anything like it.
So are these the sort of people you want protecting your kids?
For a bewildering number of people, the answer seems to be yes. We are frequently told that there is widespread public support for paedophile hunter groups in Northern Ireland, due to the perception that the police are not doing enough to curb the activities of predatory child abusers.
In Northern Ireland, of all places, we should be extremely wary of this default lurch towards support for vigilantism and mob justice.
Injecting fear - didn't we have enough of that in the past?
But it's no coincidence that such shady groups, who thrive on secrecy and threats in the dark, are flourishing. We are still far - very far - from being a normal society.
Lawlessness lurks just below the surface, frequently breaking out in brutal acts of violence - and it's actually getting worse. It was recently reported that there has been an almost 60% increase in punishment shootings and assaults from 2013 to 2017 and the level for 2017 is up 35% on the previous year.
Claiming to be defenders of communities, champions of the vulnerable, scourges of anti-social behaviour - this has long been a useful front for the arbitrary exercise of power.
Paramilitaries on both sides posed as staunch community protectors while keeping people fearful and subservient, under the cosh.
Public humiliation was one of their favourite tactics - remember the grotesque tarring and feathering of women in the Seventies?
Now, no doubt the self-proclaimed paedophile hunters would say that they are nothing like the paramilitaries. They don't shoot anyone. They claim they are on the side of good, not evil. And what could be a more noble calling than the pursuit and exposure of perverts who prey on children?
Everybody loathes paedophiles, after all: they are public enemy number one, universally feared and despised, the lowest of the low.
Therefore we should be celebrating and encouraging these have-a-go heroes who have their hearts in the proper place, right?
Wrong. These "hunters", swaggering around with their masks and aliases and narcissistic fantasies of being caped crusaders, have no right to claim the role of "judge, jury and executioner" as George Keenan so grandiloquently put it.
They have no expert knowledge, they have no authority or mandate to act on our behalf, they have no powers of detention, and they are accountable to no one. Some may have criminal and paramilitary links. In confronting and live-broadcasting images of people they believe to be sexual predators, they also risk undermining the likelihood of successful prosecution. Guilt, not innocence, is the knee-jerk presumption of the mob.
This is assuming they have identified the right place and person in the first place. One of these gangs made a bad mistake when they surrounded a house in the Springfarm estate in Antrim, terrorising the occupants - a 34-year-old woman, her mother, and her two children, aged seven and three. A neighbourhood watch co-ordinator who attempted to intervene was denounced by the mob as a "paedophile lover". But there was no paedophile there - except in their own hysterical minds.
In a separate case in Co Antrim, a man took his own life two days after he was confronted. These ugly, ham-fisted interventions are not without consequences.
Although there have been over 100 incidents reported to police by hunter groups in Northern Ireland, nobody has yet been charged. So whatever the vigilantes are doing, it isn't working.
This is not about protecting or avenging vulnerable children. That comes far down the list.
It seems their main objective is to find a target for their own rage, loathing and hatred. They'd be better off seeking psychological help for that and leave the real paedophile hunting to the police.