Sonny Dear, 19, will serve a minimum of 16 years before he is eligible for release from jail for stabbing Brian Johnstone to death in March 2009.
He had denied murder and, on trial at the High Court in Dundee, claimed he acted in self defence.
The court had heard how Dear's mother had become involved in a row with her neighbour, Mr Johnstone, who had Huntington's disease, after she arrived home drunk from a funeral.
She shouted at Mr Johnstone, 47, who was standing outside his front door and ended up clashing with her son and his friend.
Dear ran back to his house for a baseball bat but ended up returning to Adamson Place, Glenrothes, with a knife and stabbed Mr Johnstone in the back.
Yesterday, at the High Court in Aberdeen, Lord Kinclaven said the teenager had shown a "surprising level of maturity" accepting responsibility for his actions. And he said he was showing as much leniency as he could given the circumstances of the offence.
However, he said: "You assaulted Brian Johnstone who was aged 47 at the time. You stabbed him in the body with a knife.
"As you stated, the offence should never have happened. The fact remains you have been convicted of the most serious crime. Your intoxication was no excuse."
He ordered Dear to spend at least 16 years in detention.
Defence lawyer Mark Stewart said his client had initially acted as a peacemaker during the argument but had returned to his house and picked up the knife.
He said: "Sonny Dear had no role in provoking the events in the street that led to the events of the evening.
"It is regrettable that the first act of violence that occurred came from the deceased on the path throwing bricks and boulders at the group."
He said his client had hoped to "dissuade further violence" by taking out his baseball bat but couldn't find it and instead grabbed a knife.
After the hearing, Mr Johnstone's brother James, 52, said his sibling had recently given up his work after being diagnosed with the disabling condition.
He said: "My brother had Huntington's Disease and, like me, it had a big effect on his life."