Banned in New Zealand?

Well, after that helpful response I wrote to the NZ censorship office and asked them. Their report states that the film was banned because it ...

...tends to promote and support the infliction of extreme violence and extreme cruelty.

The feature showcases the most extreme forms of violence and brutality for the purposes of entertainment. The contextualizing factors, plot, and character development are weak and serve little other function than to justify greater degrees of violence as they film progresses. There are no repercussions for such brutal acts which are able to be committed at will and are intended to thrill the viewer. The overall effect is that extreme violence and cruelty is glamorized and promoted.

Excisions were considered, but, due to the pervasive nature of the problematic material, they would be impractical.