Greig Love, 20, who admitted killing Daniel O’Farrell , 21, was ordered to serve a minimum of 14 years detention.
He stabbed Mr O’Farrell repeatedly at 23 Greenlaw Crescent. Glenrothes, Fife, on September 9, last year.
First offender Love confronted Mr O’Farrell after it was alleged that that had sexually abused two teenage girls at a party.
Yesterday judge Lord Matthews told Love: “You have pled guilty to the brutal murder of Daniel O’Farrell by stabbing him repeatedly. The appropriate course of action would have been to contact the police, instead of carrying out an execution.”
“His parents had the awful experience of burying their child, his daughters will grow up never knowing him and their lives will be blighted by knowing he was murdered.”
Lord Matthews said that but for his early guilty plea, he would have sentenced Love to at least 17 years detention.
The High Court in Glasgow heard that first offender Love confronted Mr O’Farrell after it was alleged that that he had sexually abused two teenage girls at a party.
Mr O’Farrell denied the allegations and said: “I swear down on my three daughters I didn’t do anything . I cannae be doing with this sh**.”
He then went home . Later that morning Love went to Mr O’Farrell’s house, armed with two knives, and stabbed him three times in the chest and back. One knife was left embedded in his back and the blade of the other knife was left in his chest.
He died in a pool of blood.
After the brutal attack Love, who was upset and crying, went to his parents’ home at 9am and confessed saying: “Help me, take me to the polis station. I think I’ve killed somebody.”
His father went to Mr O’Farrell’s home and saw him lying crouched on the floor, dead.
He then took his son to Glenrothes police station where Love told officers: “I put a knife in him. He has got bairns.”
He later added: “I’ve got anger management issues and I black out. I turned him over and I watched him taking his last beath. I’m sad, but a part of me is proud of masel for doing it.”
Prosecutor Bernard Ablett said: “The cause of death was stab wounds to the chest. Mr O’Farrell was stabbed three times.”
Defence QC Ian Duguid said: ‘This is a rather sad and sorry case. An emotional over-reaction to Mr Love learning that there were two alleged sexual assaults on two 14-year-old girls in a house.
“This was the catalyst which brought about the death of this man. Mr Love became very angry.
“This is a 20-year-old first offender who has no record of acting in a violent fashion. He is very sorry for having reacted in this way. He acted out of character in extreme circumstances.
“He claims that Mr Farrell said he was going to take the virginity of one of the girls and then take her into the woods in a black bag.”
Mr Duguid said his client rejected a suggestion by the social worker who compiled a report on him that he ‘discussed the events with an air of bravado.”
As he was led away to the cells Love waved to family and friends on the public gallery of the court.