The shaven-headed spectator, who was wearing a Wallabies jumper reportedly brought nearby children to tears as the fragile situation threatened to erupt near the Cbus Super Stadium tunnel entrance.
The fan was then dragged away by another fan, throttled as he was dragged away from the front row.
A group of around 10 people, including several Wallabies players were involved in the scuffle.
Samu was visibly shaken by the incident.
Fox Sports commentator Nick McArdle said the Wallabies star appeared on the verge of tears.
"That is not understandable, that is not acceptable," he said of the fan's attack.
"He's almost on the verge of tears there, you can see that he's very, very upset."
Former Wallaby drew Mitchell said it was "ridiculous".
Fox Sports rugby analyst Rod Kafer said: "It looked ugly.
"It was one fan who was upset and got vocal.
"It was a high tension moment that got calmed down quite nicely."
The moment all sparked after a fan was heard yelling at Wallabies players in the background of Kafer's post-match interview with Dane Haylett-Petty.
Wallabies coach Michael Cheika addressed the incident after the defeat saying Tui had told his teammates he didn't want to play for the side anymore.
"So I hope the fan's happy," Cheika told Fox Sports.
"That's a pretty heavy thing to happen, he's just said it in the dressing room to the players now... he's not going to be playing anymore because of that incident.
"It's one thing being upset with a team... (but) what went down there was the supporter pushed Lukhan's sister.
"Lukhan didn't like that, and that's fair enough.
"Obviously that family's had a very big week and I don't think that's appropriate that that happened.
"I know the guy probably doesn't know it's Lukhan's sister but still, you shouldn't be pushing a kid in the crowd anyway."
