Forty-one year-old Raymond Shand struck David Suttle, 59, at the Horn Inn Pub in Newtown Street, Duns, on September 22 2019.
The High Court in Edinburgh heard last week how barmaid Heather Brown had told Mr Suttle to leave the pub late in the evening.
But as he was leaving, Mr Suttle was heard to insult Ms Brown, calling her a “fat b***h”.
This prompted Mr Shand to tell her: “He’s not going to speak to you like that.”
The court heard that Mr Shand then punched Mr Suttle, causing him to fall over and bang his head on the ground which led to him sustaining a fatal head injury.
Shand, formerly of Huntly, Aberdeenshire, was then apprehended by police and brought to court.
The story emerged following a hearing before judge Lord Richardson on Friday.
Shand, now of Peebles, pleaded guilty to a charge of culpable homicide.
The court heard that Shand is a farmer who has no previous convictions.
He had travelled to Duns from his then home in Aberdeenshire to spend time with his partner.
Prosecutor Mark Mohammed told Lord Richardson that Mr Suttle had insulted Ms Brown on a number of occasions.
Mr Mohammed said: “The girlfriend of the accused, Heather Brown, works as a barmaid at the Horn Inn. The accused worked as a farmer in Aberdeenshire.
“He would periodically stay with his girlfriend in Duns. Heather Brown knew the deceased who was a regular at the Horn Inn.
“When the deceased was intoxicated Heather Brown was of the view that he was a nasty drunk. He would often make cutting remarks about her weight and had insulted her after he had drinks.
“On one occasion in the weeks before he was killed, he mocked Heather Brown’s weight and suggested she was pregnant.
“Heather Brown then confided about the deceased to him.”
The court heard that on the night he died, Mr Suttle had been drinking in the pub and was told to leave.
He then made the remark which caused Mr Shand to strike him and he lost his life shortly afterwards.
Shand was also convicted of assaulting another man, Derek McDonald, by punching and kicking him on June 16, 2019 in Duns.
Defence solicitor advocate Iain McSporran QC asked the court for Shand’s bail to be continued. He said the court would be required to call for a background report as Shand had no previous convictions.
Mr McSporran also said that he’d reserve his mitigation until Shand’s sentencing hearing. But he said the circumstances surrounding the culpable homicide were such that Shand might be entitled to a non-custodial sentence.
Mr McSporran added: “I will be making a submission that a custodial sentence is not inevitable.”
Lord Richardson continued Shand’s bail.
However, he warned the accused that this did not mean he would not be going to prison.
He added: “You should not read anything into this.”
Shand will be sentenced at the High Court in Edinburgh on Friday, September 24.