I don’t know anything about the Maoris, they might be totally fine people but from their appearance as shown in movies they look like really slimy characters.
"Once were Warriors" is probably the film you are specifically referring to: it played in the US, and is based upon Alan Duff's book by the same name (the first of three books: followed by "What Becomes of the Broken Hearted" -- also a movie that had limited US release, and another one which I can't recall)
Alan Duff is a Maori, and writes on Maori social issues. "Once Were Warriors" and "What Becomes of the Broken Hearted" does indeed paint an ugly picture of Maoridom at its underbelly. "Slimy" probably isn't the right word for it: "Extremely Violent" describes it better.
That aspect definitely exists, just like "Colors" depicts a certain aspect of the Black experience in the US.
As with all stereotypes, they do not play out well in the absolute. Maori culture is rich and very exciting, Maori hospitality is legendary, their arts and technologies are truly amazing, and their bravery on the battlefield is without equal anywhere in the world.
I spend a fair bit of time with Maori organizations, most particularly the Ezekiel 33 Charitable Trust, whose mission is to keep youth-at-risk away from drugs, crime, and the gangs -- which is a mission entirely compatible with the Guardian Angels, of which I am the NZ National Director. They are a fantastic organization.
In many ways, the Maori experience with Europeans mirrors the Canadian Indian experience: treaties were put in place, and treaties were broken, and land was expropriated unfairly and their culture was suppressed: without ever once being beaten fair-and-square in battle.
I think it is this latter point that galls them the most. Their deal with the Crown makes them equals to all New Zealanders: some would argue that it makes their system of government equal to Parliament. And yet, until quite recently, Maori were treated as anything but equal.
We are now paying the piper for that.