At that time NZ Settlers had just gotten out of a very destructive war with the Maori. Maori people fought exceptionally well and some historians credit them with inventing proto-trench warfare.
The white settlers had to cry to Britain for help, and the war was so expensive the Brits basically told the settlers that they weren't getting bailed out again. In other words the KKKrakas were afraid that the dipshit Aussies would kick off round 2 with the Maori and get them all killed.