Generally, think about the situation where all (most) countries abolish borders, not just NZ or other small country. Moving is the basic human right, and the sooner we realize the better for mankind, assuming the culture of the host country is respected. Of course the culture needs adjustments to respect human rights as well.
I would disagree that is is for the better of mankind. In some cases, it could be, sure. In most cases, it eventually is not. How is it good for anyone to move from one stagnant area into a prosperous one to the point of dragging it down to be stagnant as well? Never mind the affect this has the people who are currently inhabiting the area.
Plus, it would seem to be that once a level of immigration has happened in an area the newcomers no longer feel the need to respect or to assimilate into the local culture, so they maintain their own. Hopefully they are carrying over their bad habits that led to their homeland sucking enough to force them to move, because they'll eventually want to move again. In the long term, that eventually makes things worse for those that lived there before, much like you pointed out in your first statement.
We have a long road to travel before mankind as a whole can, in masses, move about freely throughout the world without there being local consequences.
Wrong wrong wrong wrong wrong... 100 times wrong.
Productivity is the root of all prosperity. First read this excellent article: http://econlog.econlib.org/archives/2015/02/always_keep_you..... Workers become on average ~20x more productive when they migrate to the first world. Because we are capital rich and we have sane government and law and order. Imagine if you were moved to Haiti and you got stuck there. How much could you contribute to society in Haiti? You could maybe slice some coconuts on the side of the road - is that gonna make the world a lot richer? Roadside sliced coconuts? Nah, much better for you to be in first world even if you're doing a low skilled job here like delivering catering to a high tech startup. That catering company is able to produce food much more efficiently, and in SF or NYC you're able to distribute it much more efficiently, and you're part of this souped-up economic engine that's changing the world. That's why they make 20x or up to 40x more (in the case of the extreme poor) when they migrate to the first world. It's better for everyone! Economists estimate that moving from the status quo to fully liberalized migration (i.e. open borders) would roughly double global gdp - that's an insane silver bullet. That's everyone getting way fucking richer in one fell swoop.
Please see my comment here for more info: https://news.ycombinator.com/item?id=9769632
Question, would slicing coconuts on the side of the road in Haiti provide the equivalent in pay as taking a low paying catering job in the US considering and comparing elements such as cost-of-living and whatnot? There are many people living in ways we would consider abject poverty but seem to be much happier with their situation than many of the supposed better off immigrants. It's sometimes about perspective too.
I would also say the current economic status of many countries around the world suggest that "everyone way fucking richer in one fell swoop" is not happening regardless of their immigration policies. Everyone is definitely not getting richer in the US despite the years of people pouring across, what is essentially, our open border.
But hey, I'm not an economist, so what do I know?
Alternatively, should we accept that population groups that have a higher birth rate should naturally dominate future generations, or is it acceptable to fence off certain parts of the world with lower birth rates and a better natural environment?
That's a huge and unfounded assumption, though.
Poor souls like the author of this article are caught in the middle. They don't have representatives in the traditional views camp and the multicultural views camp considers them to be secondary since they're not as likely a voting block once they come in.
The problem is that the thing is a moving target. When a lot of still alive people where born 'culture' was: 'a black woman was not supossed to sit in the best places of a bus', 'the children roam free with their friends and dogs and can go everywhere' and 'Is acceptable if I slap my wife in the face sometimes because I feel frustrated for the work'. Yes, this was a small part of the tradition not so long time ago.
Each generation have been educated in a different point of view about what was acceptable or not. What 'culture' should be honored for newcomers?. West coast 1966? Sometimes 'culture' is just plain wrong and should not be respected.
Just having an immigration system that is followed legally would be a lesson in culture that we've currently abandoned for political purposes.