One of the men told Thompson to, "Calm down, c***".
Thompson, who pleaded guilty to assault at Christchurch District Court, admitted punching the man twice in the head.
The pair fell into a car, causing $900 in damage to its door.
At court today, through his defence counsel Jonathan Eaton QC, he was granted a discharge without conviction.
Thompson, the court heard, felt surrounded and intimidated by the crowd.
When the complainant phoned the police to report the assault, Eaton said the man admitted he shouldn't have used such offensive language towards Thompson.
The complainant suffered a cut to his nose and two large lumps on his forehead. Thompson received a black eye.
Eaton said in spite of Thompson's substantial fraud offending, for which he served jail time, the offending was out of character.
Thompson later admitted it was a "stupid and inappropriate" response to a situation where independent witnesses identified him as the aggressor.
After his release from prison in 2004, he vowed to never to return to a courtroom again as a defendant.
The Salisbury Street Foundation (SSF), a privately-run residential facility that helps prison parolees reintegrate into the community, helped Thompson turn his life around.
Thompson has gone on to establish a successful car dealership in Christchurch.
He has also been an SSF board member since 2013 and does youth mentoring with other organisations.
Eaton argued a conviction would mean Thompson would have to give up his valuable mentoring roles and work he does in the community. It could also affect his biannual trips to Japan to buy cars.
Judge Brian Callaghan said the incident was clearly a "fall from grace" for Thompson.
But he was satisfied the direct, and indirect, consequences of a conviction would outweigh the seriousness of the incident and that a discharge without conviction could be entered.
The judge ordered Thompson pay $948 in reparation for the damage to the car door, and a further $1000 as emotional harm compensation to the complainant.