You're wading into an extremely, incredibly, magnificently dicey topic here, one with a history of contention that dates back a long time. What is more or less certain is that yes, like many Polynesian peoples, the Maori have a history of cannibalism. That much is not up for debate. And even among Polynesia, Maori cannibalism seems to have been particularly widespread. Among the Rapa Nui of Easter Island, to pick a random example, it seems clear from archaeological examination that human cannibalism was relatively rare, as it was treated as a ritual event: there are no evidences of human bones found in any domestic ovens; only ceremonial. However, from the moment James Cook arrived in New Zealand, he reported firsthand accounts of regular human cannibalism. Nevertheless, the British were fairly tolerant of the Maori in general and when the British formalized the colony with the 1840 Treaty of Waitingi, the Maori were equal partners. Of course, this peaceful coexistence lasted only a few decades, and by the latter half of the century tensions were increasingly fraught. Whatever their original intentions, the white settlers of New Zealand are ever more populous and prosperous than the Maori. By the 1960's, New Zealand experienced much the same general uproar as the rest of the world, and pro-Maori groups began to assert themselves in both the wider society and in academia. As is fairly common with underrepresented groups, they were very tired of hearing white people pass judgement on them and their cultural history. So it became sort of an awkward topic, with many Maori advocates chafing angrily at accusations that their ancestors regularly ate one another. It's still an awkward topic, in that respect.

Nevertheless, it's almost certainly the case. Yes, the Maori practiced cannibalism. It was most commonly, or possibly exclusively, done to enemies captured in battles. No, they didn't lust for human flesh, but yes, they did take pride in eating their foes. It was very frequently linked with revenge. It also has a great connection to their mythology, which is, by the way, incredibly interesting. (There's a good round-up of that connection here: http://nzetc.victoria.ac.nz/tm/scholarly/tei-BudAbor-t1-body-d1-d2-d3.html )

The most comprehensive book on the topic is Paul Moon's "This Horrid Practice," which sounds a lot less professional than it actually is. (And indeed drew some flak for the tenor of his assertions, though not their veracity.) I'd recommend it highly.