A man jailed for violence told his victim he was sorry, but it was "a Mongrel Mob thing", before beating him unconscious, Masterton District Court heard.
Anthony Sene Fa'afo'i, 20, was sentenced to 22 months in prison for injuring with reckless disregard for safety, and two breaches of community detention.
Judge Bill Hastings said Fa'afo'i and two others had been drinking at a Masterton hotel and had left together "late in the evening".
The group had stopped at an intersection and Fa'afo'i "told the victim you were sorry and that it was a Mongrel Mob thing", the judge said.
"You then proceeded to hit him about the head, causing him to lose consciousness".
Injuries included two large cuts to the victim's face and a cut under one eye.
One eye was bruised and swollen shut, and the victim fell to the ground, suffering cuts to his elbow and hip, and was rendered unconscious.
Judge Hastings said attacks to the head "are inherently risky" and can lead to brain injury, adding that Fa'afo'i's comment beforehand was an aggravating feature.
"This implies some pre-meditation on your part as well as gang motivation."
Fa'afo'i had pleaded not guilty to the assault, and took it to trial, where he was found guilty.
Even after the verdict, Judge Hastings said, "you continue to protest innocence".
The judge granted leave for Fa'afo'i to apply for home detention, should a suitable address be found, and imposed six months post release conditions, including alcohol counselling.