Mr Bishop then lost the entire amount the next day when an associate took the money from his pocket while he slept in a sleep-out at a Napier address.
He and a friend failed to find the associate the next day and when he told his uncle what had happened an argument broke out and Timu punched him in the head; causing him to fall against a metal fence and rip his ear.
Mr Bishop's friend was still looking for the associate at a Napier address when the defendant arrived with his nephew, who had told him he thought she might have been involved in the theft.
She denied the accusation and Timu then said he would follow her to her house because he wasn't leaving without his money.
At her house, she agreed to go with the pair in Timu's vehicle to try to find the associate, but this was unsuccessful.
The defendant then told her he would take her vehicle as security until the money was returned.
She told her father what was happening and, after he had argued with Timu for some time, her mother eventually called police.
When police arrived Timu explained that his nephew had been "rolled' and he was trying to sort it out.
His defence lawyer, Eric Forster, submitted Timu was remorseful and had not offended since 2003.
"This man does good work in the community. His explanation to the probation officer was that people who have more dysfunctional lifestyles dragged him into something he should have known better to become involved with."
Judge Rea said Mr Bishop's injury was serious, requiring stitches to repair a 3cm laceration to his ear, but added that Timu had kept out of the courts for almost a decade and a half despite his "colourful background".
"I just hope the irony of all of this isn't lost on you. You claim to be a crusader to help people getting involved with methamphetamine. Yet on the other hand you are prepared to fund, in the thousands of dollars, the purchase of cannabis."
White Ribbon campaign manager Rob McCann said organisation did not condone any violence but it was important those using violence were encouraged to stop.
"As this example demonstrates, it's not an easy task if you've grown up with violence and used violence to solve problems. It is not an easy task to reject that way of solving problems and dealing with life."
Mr McCann said the defendant was never a White Ribbon ambassador, rather a supporter of the kaupapa at a grassroots level, but would have been stood down if he had been an ambassador.
"We have to send a clear message, which I think the judge has done, that this violence is unacceptable but also that there is redemption out there.
"There is the ability to use life for a better purpose and that's clearly something that Rex is trying to do but it's a struggle."
As well as advocating for White Ribbon's anti-violence message, Timu had been employed as project manager and whanau development manager for nationwide change trust Waka Moemoea.
Sociologist and gang expert Jarrod Gilbert said the defendant's conviction did not negate his pro-social community work and messages.
"The great difficulty people like Rex have got is that positive change is never easy and rarely is it absolute, at least initially. Changing their behaviour . . .happens over time.
"The endeavour to turn gangs around and turn a new leaf with certain individuals and in certain chapters of gangs is genuine. But to expect that to happen as a smooth and clean process without the odd hiccup along the way is just unrealistic."
Violence in gang culture was "without a doubt" decreasing, Mr Gilbert said, but this was as much a family matter as it was a gang one.
"It's come about because of a dispute in the family, not in a gang. As a leader of course people look to him to set an example but in a realm and world of gangs, the violence that's been displayed here is at a very mild end of the spectrum."
Timu will serve seven months' home detention at his home address in Flaxmere.
