"I accept that there is a basis for the suggestions that you overreacted to a sexual overture,'' Justice Toogood told Knight.
He said Knight repeatedly punched, kicked and stomped on Mr Tunnicliffe, leaving him unconscious - a "spontaneous overreaction'' which was brutal and sustained.
Justice Toogood said Knight left Mr Tunnicliffe unconscious, stole some of his property and made no attempt to get help. He was picked up by police a short time later wearing Mr Tunnicliffe's bloody shoes.
Knight's lawyer Ian Farquhar said his client accepted there was no excuse for his actions and he had entirely overreacted.
He said the chances of rehabilitation for his client were good if he was able to work through his childhood issues.
Justice Toogood acknowledged Knight had accepted full responsibility for his crime, was profoundly remorseful and had pleaded guilty to the murder at an early stage. He had no history of violence.
He said Knight had a difficult childhood, which included the suicides of his father and sister, and was estranged from his remaining family.
"You have no moral or social compass and few social skills,'' he said.
Justice Toogood said the sentence was a suitably harsh penalty for such a young man.