As a fellow Kiwi I know what you mean. I don't want him to be extradited and feel the precedent of cooperation on something like copyright is a betrayal of our sovereignty, but at the same time, there's so much detail to this case and there is so much bullshit swirling that a (lengthy) trip to the supreme court in the US would seem to be worth the risk if it can establish some precedent which moderates the ever-strangling enforcement of IP legislation at the moment.
Extradition is not a violation of sovereignty; it's an affirmation of sovereignty. The US has to politely ask for the accused to be turned over and the NZ courts will decide whether the request is legally valid under New Zealand law.
