A few points:
1. To call "enjoy your life" divisive does make me wonder.
2. This article about a rejected atheist ad is unusual in that, unlike the others, it doesn't state the intended words. Were they the same as in the British example? Many alternative slogans have been used on buses, all reasonably mild-mannered. It would be nice to see the wording this time, so people can judge for themselves with whether NZ Bus was right.
Edit: thanks, j.mills (463683). Boy is my face red.
3. The Human Rights Commission? Is this even a matter of legal rights? No doubt a string of posters will mention in the coming hours that private companies can run what they like. At any rate, they certainly should refund any bills for services they decide not to provide (at least on the days for which they pulled it), but I bet that that's the limit of their legal liability.