This guy was unfortunate in tripping some sort of alarm for them. I've travel NZ<->US approx twice a year for going on 15 years now and have never so much as been stopped. I always ask for the frisk and grab rather than the microwave scanners (I'm thinking about the TSA folks who have to work there) and have been to many 'hacker' conventions while in the US and never triggered anything. I guess I fit a profile as a 'known'... rather than unknown. Maybe someone the guy spoke to at this conference is someone they genuinely want to know everything about. This doesn't make it OK but it's quite likely some specific thing that set it off for them
All of which to say you'll probably be fine and I don't imagine being a US vs NZ national will make any difference as to whether you get the stazi treatment or the wave through.
Also FWIW I'm usually a more worried about missing my flights due to unnecessary searches on the TSA side of things (combining a special breed of stupid with a dangerous type of wilful paranoia) than on the NZ side (more of your basic 'just following orders guvn'r' type of stupidity)
All of which to say you'll probably be fine and I don't imagine being a US vs NZ national will make any difference as to whether you get the stazi treatment or the wave through.
Also FWIW I'm usually a more worried about missing my flights due to unnecessary searches on the TSA side of things (combining a special breed of stupid with a dangerous type of wilful paranoia) than on the NZ side (more of your basic 'just following orders guvn'r' type of stupidity)