The New Zealand MPs performing the traditional Māori haka in parliament as a protest are not saying “Kamata” (蒲田).
Around the 10-second mark, a female MP tears a piece of paper and loudly chants “Ka mate! Ka mate!”
This comes from a very famous haka piece called “Ka Mate.” In the Māori language, it means “I die! I die!” (or “It is death!”). Because the pronunciation of “Ka mate” sounds incredibly similar to the Japanese place name “Kamata” (蒲田), it is highly likely that it just sounded that way to you (a classic case of “soramimi,” or a phonetic mishearing).