Was this email refusing you a visa? Or did the CO go on to say that you would therefore need to apply for a character waiver? Or was this a potentially prejudicial information email? - that is, you were asked to reply with any further relevant information or comment?
Possibly (I don't know) the court would have had the power to sentence you to a three-month term of imprisonment for what you did.
http://www.immigration.govt.nz/opsmanual/43627.htm
You should be aware that in the last two or three years, the NZ government are treating driving offences increasingly seriously. Your post above gives the impression of thinking that demerit points are not serious - though they are ALL given for breaking a law, and, on the road, therefore possibly surprising and/or endangering someone else. Then you drove while suspended, which again you must have known was breaking the law. This is not nothing. Most people go through their whole lives without getting taken to court. INZ's attitude may be that if you are happy to break some NZ laws, you may have the same attitude to immigration law. You may think they're wrong, and that people shouldn't feel like that about you, but the NZ government and legal system have the power, so what they say, goes. NOW do you see the kind of approach needed from you here? - you have to accept that you were in the wrong, and may therefore get refused the visa you want. IF you are being given the chance to apply for a visa waiver, you have to write a letter explaining your wrong actions, and accepting that your reasons at the time were wrong, and that you have changed since then - which in your case may be difficult as it is such a short time since this happened. And you have to give character references from people of standing in your community stating that you are a well-behaved person who contributes to society.