At sentencing Judge Geoff Rea spoke of the "irony" of sentencing Timu after his pro-social agenda.
Although he had tried to make a better life for himself and his family there was "no doubt" he had used his gang status as an intimidation factor during the offending, the Judge said.
His defence lawyer, Eric Forster, submitted his client 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 noted Mr Bishop's injury was serious but accepted 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."
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."
White Ribbon campaign manager Rob McCann said Timu had been a supporter of the kaupapa at a grassroots level but would have been stood down if he was an official White Ribbon 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."