Harris will be sentenced on Friday but Justice Nigel Sweeney has already made clear the 84-year-old can expect to go to jail.
The entertainer is the second person to be convicted under Operation Yewtree established in the wake of the Jimmy Savile sex scandal.
Publicist Max Clifford was sentenced to eight years' jail in May after being found guilty of eight indecent assaults against four young women.
Ms Monahan said the likes of Savile, Harris and Hughes had all thought they were "above the law".
"When I went public four years ago, it was still taboo to point the finger at a celebrity for having committed a sex crime," she said.
"People before me had tried and failed. Some named their perpetrators, and nothing was done, others came out and said something had happened, but didn't dare name the people involved. All of us experienced a public backlash. You'd think the victims were the perpetrators by some of the reactions.
"Hopefully this last few years of people speaking up, and these people finally being caught out and made to pay for their crimes will have the effect of making people realise they can't get away with this s***, and they will think twice before hurting a kid."
Ms Monahan also paid tribute to Harris' victims for having the courage to come forward.
"So congratulations to today's winners, the girls in the Rolf Harris case. Not just the few who managed to get charges," she wrote.
Hughes was sentenced in May to a maximum of 10 years and nine months, with a non-parole period of six years, for the sexual and indecent assault of four young girls.
- AAP