He said the main cause of the altercation was George Moala's public profile as a rugby player.
"One of those perils for sporting figures, and people they choose to spend time to socialise with, is their heightened profile can be a lightning rod for the drunk and disorderly," Mr Wharepouri said.
"Some of those drunks, whether they're driven by some personal insecurity or petty jealousy, think it can become a sort of sport to bait, tease, cajole or insult sporting figures.
"And some of those drunks are prepared to go to the point where they're prepared to try and physically better the sporting figure."
The bar brawl, during which bottles and chairs were thrown around the room, saw one of the Samoan men - Clifford Matoka - sustain a nicked artery in his neck and he was hospitalised after suffering significant blood loss.
But Mr Wharepouri said it was his friend Damian Leota who started the fracas with his "oafish behaviour".
When his attempts to "call people out" for a fight were unsuccessful he turned his attention to George Moala, the defence lawyer said.
"There's no doubt my client [Suia Moala] assaulted somebody, he admitted as much to police. Can the Crown prove beyond reasonable doubt that he was not justified in doing so?" Mr Wharepouri said.
"He was reacting so as to defend his younger brother. He honestly believed his brother was under attack."
George Moala's lawyer Paul Wicks, QC, did not rely on an argument of self-defence.
He said the rugby player stood up when the original fight broke out but was held back by his girlfriend Vava Fosita.
"The only other involvement that occurred was downstairs when his partner was struck at the doorway," he said.
CCTV footage showed him and others pursuing Mr Leota along the pavement before running off when police arrived.
He was apprehended by officers and told them he had "retaliated" because of a punch thrown at Ms Fosita.
Judge Rob Ronayne will sum up tomorrow and the jury will begin deliberations.
