He told her: "I don't care, the cameras are on us, carry on."
Stafford said Hori was cutting off her air supply and a stern response was needed to bring him back to his senses.
"I just lifted my knee and went into his balls." Hori then grabbed his testicles in pain, stood vacantly for a second, then "wobbled off."
"For the rest of the game he just stood underneath the goalposts."
Tauranga man Terry Leaming, who ran for Tauranga Mayor in 2007, plays Hori - an overweight, raucous, hyperactive, pie-munching Steamers fanatic.
Photographer Glenn Taylor said Hori attacked Kahu twice, once as the players came on to the field and then again later in the game.
Hori held Kahu's beak and pushed her head from side to side, Taylor said.
"She was saying 'stop it, I can't breathe.' He wouldn't stop, so she kneed him in the nuts." Taylor said spectators were stunned. "They didn't know what to make of it."
Stafford said Leaming approached her after the game to apologise.
Stafford said no-one from Hawke's Bay Rugby Union has called her since Tuesday. Her neck and upper back were hurt and she has to cover the cost of physiotherapy herself. "I was in a neck brace for three days. The only way I could hear or talk or breathe was through my beak."
Hawke's Bay Rugby Union Commercial Manager Jay Campbell said Stafford had volunteered to be mascot for the day, as it was normally too expensive to take mascots to away matches.
Hawke's Bay Rugby Union Chairman Kevin Atkinson said he never saw any scuffles at Rotorua. But he said any kind of mascot fight was disturbing.
"It's disappointing because you try and keep the spirit of these things friendly," he said.
Long-serving BOP fan Casey Thomas was at Eden Park for last night's clash between BOP and Auckland.
He said Hori is normally "good fun" and adds a lot to the game's atmosphere.
BOP Rugby media liaison Ross Everiss said Hori is an unofficial mascot. "Our official mascot is a character called Steamy."
Hori was not at last night's match and does not travel with the BOP team officially, Everiss said.
When the Herald on Sunday tried contacting Leaming, a man called Terry answered the phone but claimed not to be Hori.