Kiwi hostilities towards Australians are deep-seated and they are not a recent development. The bitterness has come to the attention to Aussies here for the World Cup because the two nations are placed in a position of drinking, competitiveness, and being placed next to each other at a game for several hours is likely to result in spitting, etc. The fact that it can happen to multiple people, and because the issue is 'timely' because of the disparity in treatment of Australians, we might expect the media to comment. But my experience tells me that there is deep-seated and long-term issues with NZ's collective self-esteem. Let me give you a flash back to when I first came to NZ in the 1990s.
Experience 1: Having just landed in Auckland, I made the mistake of presenting a $A10 instead of $NZ10 to the car park attendant. Yeh, you'd think I'd realise that I was in the wrong country, but they are so similar, it did just feel like I was in Australia, most particularly perhaps because I was in a mundane looking car park and tired. The response by the attendant was less than courteous. As if I had insulted her.
Experience 2: Talking to a NZ'er in a bar he was surprised that I had pleasant things to say about NZ...as if we were only negative about the place. I must admit to joking with an American about how backward Wellington was in 1990. Why? Because there were weatherboard homes next to the airport, and so close to the city. NZ cities are far more cosmopolitan now, and there are many more choices to go. And unlike at those times, you can now go out without people being polarised by the rugby....as if that was life. The reality is that...NZ is boring, quiet and 'undeveloped'. That is a point of derision if you appreciate the excitement, fun and choices of a big city. The feeling is the same if I fly from Tokyo to Sydney, my home town. NZ is more boring, and I can't even credit it with being different.
Experience 3: In the early 1990s I bought a Korean girlfriend to NZ. We went to a bar and joked at a bar that I needed to split my Australian and NZ coinage. I expected a barb of some type, and even set her up for it. I was surprised when her 'We expect that from Australians' was far more bitter than I expected. No mistake; she was adamant when I queried her. I wondered what I'd done to offend her. Two possibilities occurred to me at the time. (i) She was a racist and disliked that I had bought a Korean into their bar, (ii) She resents tourists because her local customers resent tourists, and I was an Australian, so that was worse. (iii) I failed on both issues.
Experience 4: I was listening to the radio when I heard some radio station play an advert with the advertiser saying 'Product on sale....come and get them before the Aussies do'. This was very funny to here, but clearly suggests even the advertisers see a deep-seated disdain for Australians they can use.
In the end, you just learn to shut up. They don't even know you're an Australian unless you tell them. Clearly not all NZ'ers are too proud to love Australians. My mother's boyfriend is NZ. He's a charming guy in NZ when I met him here, but so uptight in Australia.