Ratings amuse me sometimes. Some media receive stricter ratings (as in M, R, NC-17, etc) without seeming terribly bad. Others have a much higher level of violence, language, or whatever else determines a need to protect those who should be protected.
I am actually impressed that New Zealand would nationally ban a game considered indecent. They stick by their principles. If we really believed media was supposed to be unsuitable for certain audiences then affixing a rating is hardly enough to protect the innocent or dissuade the consumers.
How many other countries would be that bold in defending principles of decency? I doubt you'd see that in the Americas, nor would anyone stand for that in any European nation.