Mr Rippon, a Black Power leader and member of the gang since the 70s, died in hospital after being assaulted at a house in Rimu St, Gonville, last year. He was a founder of the award-winning Matipo Development Trust which helped vulnerable families in Whanganui.
The fatal assault came after a puppy went missing, and Mr Rippon was asked to help look for it, Justice Clark said.
"He later found out where it was and went to that address. With the consent of the people who had earlier found the puppy and were looking after it, Mr Rippon took the puppy and returned it to its owner."
This led to the assault. At the end of the attack, Mr Rippon was lying "unmoving" on the ground.
Justice Clark said Tyrone William Madams swung a spade down on Mr Rippon's head at least one more time "as he lay defenceless on the ground".
Mr Rippon was left unconscious where he was, and later died in hospital from "extensive head injuries".
Madams and other members of the group were found by police soon afterwards. Madams had suffered a serious cut to his hand from breaking a window, and required surgery.
Crown prosecutor Harry Mallalieu said Mr Rippon's family's loss was "immeasurable".
Defence lawyer Debbie Goodlet said Madams committed the murder out of "reckless disregard" as opposed to attacking Mr Rippon with an intent to kill him.
"His instructions have always been clear: 'I feel guilty, I am guilty.'"
Before sentencing, Justice Clark told Madams he could have a seat, but he declined.
"I don't deserve to sit, miss," he said.
Justice Clark said Madams knew the victim well.
"You and Mr Rippon - Uncle Rip - were close."
She considered if Madams could attack Mr Rippon in such a way, despite being close to him, "It is reasonable to assume that those who are strangers to you may be at even greater risk. "Protection of the community features strongly in my mind."
She noted Madams was "extremely remorseful", although pointed to a concern in a report quoting Madams as saying if it has been someone else "It wouldn't be that bad".
However, Justice Clark accepted the explanation Madams meant his own grief wouldn't be so bad. She believed Madams would still have remorse if it had been someone else.
Justice Clark finished the sentencing with an "observation".
She noted Madams himself had had an experience being hit on the head with a weapon, with the difference being that he woke up afterwards.
"How normalised these acts of brutality have become for you and others who have been similarly exposed and similarly offend."
The prison sentence would be beneficial for him, she said.
"You will have the opportunity to embark on what you have been trying to achieve but have found impossible."
Justice Clark said Madams would be able to distance himself from his "dysfunctional life", would have a chance to work towards an education, and would benefit from monitoring of his safety and mental health.
She sentenced him to life imprisonment with a 12-year non-parole period.
