Balle said his nephew asked the man three times if he was allowed to buy food, and it was only after the third time that the man said "well I guess you can now".
"What I really want to know is what was your motive behind confronting him? Do you expect him to bow and walk away? Did you not expect him to ask you the same question if you were from here?," Balle added.
"Well to answer your question lightly ... he attended the kohanga at Bayswater Primary, his mother, myself and two other sisters attended TGS (Takapuna Grammar School). His aunty attended Hauraki Primary, Belmont Intermediate along with his cousins and his grandfather resided in Wakakura while in the navy ... so 'Mr Local' your answer is yes. He is from here."
Responses to the post were generally supportive of the nephew.
One said they were sorry the man had to deal with that kind of behaviour, and another said it was a shame this had happened in "our beautiful little suburb".
"Unfortunately happening far too often here in Devonport, good on your nephew for standing his ground."
Devonport Primary Principal Beverley Booth said she had only just been made aware of the post and the reported incident when the Herald contacted her on Sunday.
"I am saddened and sorry to hear about this and my thoughts are with the whanau involved," Booth said.
"This is completely out of character for our school and certainly not in keeping with our values of belonging, respect and excellence, which we strive to reflect throughout our school culture."
Booth said the annual school fair was a "special community event where everyone is always welcome".
"Yesterday everyone pulled together to reorganise the event to make allowances for the dreadful weather and we were very grateful that so many people ventured out in the wind and rain to support us," she said.
Booth said she was investigating what happened and would be making contact with the family directly.