Based on my own experience (and I only have anecdotal evidence to offer here), I'd agree that Aucklanders as a whole are fairly tolerant, but some parts of the city are far more accepting than others. When I was growing up in south Auckland - Manurewa, Wiri and Papatoetoe - my mixed heritage was never a hindrance and was very rarely a talking point (although my unusual name has always drawn attention, but that's not altogether related). The only times I've faced racist comments in Auckland have been in the inner suburbs, and while they only occurred a few times they were particularly unpleasant.
What I've found very interesting (for lack of a better word) are the reactions from strangers to my two children. My firstborn inherited my latent white genes and has pale skin and light hair, while my second child has dark hair and olive skin like mine. The eldest is five years old and nobody has ever asked me about his ethnic background. The youngest was only seven weeks old the first time a stranger asked where we were "from".
People in Auckland are accepting of diverse ethnic backgrounds, yes, but if you aren't white it's still something to be noticed and commented on.