This is going to come as a HUGE SHOCK to our American friends out there, but there is a strong and vocal anti-Halloween contingent in New Zealand. I KNOW! Why? How? Usually you think New Zealand, and you just automatically think, better. I mean, there's even a dish soap flavour named "New Zealand Springs." Not a lot of countries could be a successfully marketed aroma. This shocking cultural misstep (alongside whatever it is they serve me when I ask for nachos), was my first real "Brand New Zealand" disillusionment.
This family's gonna do the crane move on your bad attitude New Zealand!
There are a variety of complaints. First and foremost, what I hear is that it's an American (and therefore automatically really bad) tradition that's being foisted on the unsuspecting children (parents) of New Zealand. I get it! America has done a lot of crappy-crap to the planet. I wasn't so pleased living in America, so now I live in New Zealand, so I get it! BUT! I am still American (which a lot of people seem to forget when telling me how terrible Halloween is simply because it, like me, is American) and there's not many aspects of our culture that I feel comfortable celebrating out in the wider world. So, I think you should let me have this one. And if you don't want to play along, that's cool. I do think you'll be missing out on a helluva lot of fun though, so open your mind and let me try and convince you.
Let's go to the moon!
Some background. I grew up in the deep South in a very small, Christian and conservative town. My parents were very non-traditional. We were poor at a time when it was really important to have expensive jeans and all your Christmas presents wrapped in matching wrapping paper from the fancy department store. We didn't go to church. Most holidays highlighted all the ways we didn't fit-in. I was far from alone in this alienation. 
It doesn't have to be all about sugar! Banana ghosts for crying out loud!
BUT! Halloween was always the great equaliser. Everyone was invited. Everyone could participate. You didn't have to be rich or white or Christian to have a great Halloween, all you needed was a little bit of creativity. In fact, for that day, you could turn yourself into ANYBODY. You could be the president, or an astronaut or a bumble bee or a super rich guy. The most egalitarian holiday ever. Kiwis are into that, right?
The other thing I hear is, "It's rude to send your kids out begging for candy! Give me candy or I'll do a trick on you!!" Ok. I can see how this one would be a bit tougher if didn't grow up in the Halloween culture. I got all the candy as a kid, so now, as a grown up, I'm super excited to give that candy back to the world. You don't have the buy-in, fine. But surely it's worth $10 a year to have your own personal parade of cuteness and creativity coming right to your doorstep? These kids (hopefully) worked really hard on their costumes, so I don't really see it as begging. And by the way, I have a strict no costume, no candy policy. But I will soften if they can tell me a joke or do a dance.
Other than that, it's really more vague arguments about how it's just not a New Zealand tradition and bah, humbug. Well, so? New Zealand isn't really teeming with celebratory holidays, why not take the time to have a bit of fun? I've never heard anyone decry Blossom festivals or Diwali celebrations or even Dia de los Muertos. Which brings me back to Halloween = America = Bad, which makes me sad and sad for my 50% American kids. BOOM. Guilt bomb. 
How can a kid in a Robin Hood costume made out of paper be anything but good??
I guess the other two main detractors are the commercialisation and the sugar. Which, yeah, you can go crazy and spend a lot of money, but that's a total choice just like in every other aspect of life. And the sugar, welllll. “He that is without sin among you, let him eat the first easter egg."
Ok fine, the Iron Man costume is pretty lame and commercial, but whatev, he got if for Christmas :)
So! I have one last point. I always see all these nostalgic posts about how before social media, you knew where your friends were because there was a massive pile of bikes outside a house and how we used to know it was time to go home because the street lights were coming on and how kids learn so much from roaming the neighbourhood with their friends. Well, Halloween helps with that. It gets all the neighbours out and talking to each other and laughing at the costumes and meeting all the other kids on the street and your kids find new buddies to hang out with and that's good. And healthy. And FUN.