The playful bottlenose dolphin was said to be displaying intimidating behaviour, leaving people battered and bruised, and had trapped at least six swimmers out at sea since he made Gisborne his base.
But Hawke's Bay environmentalist Dave Head, who has spent a lot of time with Moko over the past three years, said the reports were nonsense.
"Some websites are now starting to say he is a sexual predator. So how come no one has seen him with his willy exposed? No one."
Mr Head repeated his call for a guardian to be appointed to protect the mammal, particularly as thousands of visitors swell Gisborne's population during summer.
An extensive study into solitary dolphins by Dr Lissa Goodwin and Margaux Dodds of the Marine Connection, an international dolphin and whale protection agency, argued that in a few cases, the need to protect individual dolphins has resulted in the appointment of exclusive guardians, whose task it was to look after the wellbeing of the dolphin, managing interactions and ensuring that distress and/or disturbance to the individual was minimised.
For Moko's protection, the Department of Conservation has said it will look at bombarding the thousands of visitors with information about the dos and don'ts of swimming with Moko.
The department also said it would hire an "advocate" who would patrol the beaches informing people about Moko.
