Sparked by the Napier-based Sensible Sentencing Trust, the rallies were staged in the wake of the Crown withdrawing a charge of murder against the pair and replacing it with a charge of manslaughter.
Three-year-old Moko was found to have died as the result of "multiple blunt force traumas".
"In New Zealand we have a problem and we need to acknowledge it," Ms Parsons said.
"Our children are dying."
She told the gathering, many of whom were bearing banners and placards, that over the past 25 years "abuse, neglect and maltreatment" had claimed more than 200 children and that last year was one of the worst on record.
"Moko, your death has united a nation in grief and horror at what happened to you," she said, adding it would become the "catalyst for change".
Napier City Councillor and former police officer Keith Price drew several loud bursts of applause during his address to the crowd.
He said afterwards he had a speech prepared but put it to one side and let his emotions produce the word instead.
"I have been involved in cases of child abuse and it is horrific - it the worst thing that can happen and if this (the Moko case) is not murder then I don't know what is."
He also vented his frustration over the right to silence issue.
"If a child has injuries you must explain - the right to silence must go out the door," he said, adding he would be fighting to see a change in that law.
Mr Price also drew a loud response of agreement when he said he did not take a soft approach to such crimes and that in such extreme cases there should be no "three strikes" rule.
"It should be one - you do not walk out on the streets again."
Napier MP Stuart Nash also gave an impassioned speech, and was clearly taken by the emotion of the moment when he spoke about what happened to Moko.
"It is absolutely beyond me - it may not be Labour policy but I take the view that if you murder a child you should go away for ever."
There were cheers of support.
"We have got to speak up because as adults it is our responsibility to stand up for children."
There was also a strong response to a speech from 12-year-old St Patrick's School pupil Charlotte Grant who wrote it for a speech competition as she wanted the issue of child abuse to be more widely addressed.
She said the statistics were "outrageous" and as Kiwis "we can be proud of our All Blacks but we can't be proud of this".
The numbers of child deaths reported made her "super sad" and she called for tougher sentences.
"Together we can make a change."
