"On more than one occasion, Nixon referred to the 'permissive' environment that surrounded his offending," noted panel convenor Judge Michael Crosbie.
"In the board's view, Nixon's responses evidence why further psychological treatment is necessary and is likely to be ongoing for some time. In the board's view, several of Mr Nixon's responses evidence a continued lack of insight into his offending, particularly around issues of consent."
The attacks occurred between October 2009 and July 2012 and the Dunedin District Court heard at sentencing that many of the victims were friends of his then girlfriend.
He attacked them as they slept or when they were drowsy or under the influence of alcohol or drugs.
Victims provided harrowing accounts of how their lives had been affected by the trauma Nixon inflicted.
One said she did not feel safe anywhere in the world and told the court she had been sentenced to a lifetime of flashbacks, panic attacks and counselling.
Three of the victims had contemplated suicide.
Nixon admitted 13 charges in court — six counts of rape against five women, three counts of sexual violation, two counts of sexual connection with a person aged under 16 and two counts of indecent assault.
Counsel Michael Bott argued the prisoner could be released to a Kapiti Coast property and while that was declined, Judge Crosbie acknowledged Nixon's strong support in the community.
There were some misconducts early in Nixon's prison stint but his behaviour had since improved, "evidencing perhaps some maturity as far as his sentence is concerned", the judge said.
A psychologist, who had met with the prisoner a dozen times, said the next practical step would be his transfer to self-care units and a "slow reintegration".
That would be a matter for Corrections to consider, the Parole Board stressed.
At the hearing, Nixon claimed his attitude to women had changed.
His relationships in the past had been based on sex, but future ones would be based on friendship, he told the board.
Nixon will see the Parole Board again in a year.