A vigilante child protection group has been strongly criticised by a High Court judge after it confronted and aggressively interrogated an intellectually disabled man who arranged to meet a 13-year-old girl he met on the internet.

The group carried out a sting operation on the man, who is brain damaged and a ward of court, and posted a video of their encounter with him on Facebook.

President of the High Court, Mr Justice Peter Kelly, who manages the Wards of Court list, was alerted to the incident yesterday and ordered Facebook to remove the video by this afternoon.

The video was later removed by the social media company as it breached "community standards".

The judge today described the actions of the group as "appalling" and said it had serious consequences for the man who was described as vulnerable and lacking mental capacity. His carers said he was distressed and suicidal after the incident.

The court heard the man lives in a residential placement and is addicted to internet sites, particularly dating sites. He made contact with a woman he understood to be 19. Despite stopping contact when told she was 13, he later agreed to meet her for a hot chocolate.

When he went to meet her he was met by two women and three men, grabbed by the arms and aggressively questioned. A video was then posted on social media.

Gardaí, who were aware of the man's intellectual disability, came on the scene and took him away for his own safety.

As the video had been viewed by tens of thousands of people there was a concern for his safety and that of others sharing the same residential care, the judge was told.

Mr Justice Kelly made orders preventing any unauthorised person coming within 200 yards of the care facility. He said people with intellectual disabilities needed to be treated with respect and dignity and the last thing they need is to be "confronted by a baying mob screaming for vengeance against a person who because of their disability cannot have mental intent of a deliberate type".

He said he presumed the group did not know the man had an intellectual disability and is a ward of court. The judge said he hoped that if they knew that, they would not have done what they did. The video, he said, made it clear these people were about "a particular task" and did it in a way that was "very frightening" and a huge setback for the man.

The judge said the man had used the internet hoping to meet a "lady friend" but had only met charlatans, including one who got his bank details from him. His use of the internet had been supervised but he managed to evade the supervision of his carers on this occasion.

Mr Justice Kelly said he would make orders preventing the man having any phone or internet access as it had proved so detrimental to him.