.... of the New Zealand Māori that was traditionally used to prepare a war party for battle as well as when groups came together in peace. Haka are a fierce display of a tribe's pride, strength and unity. Actions include violent foot-stamping, tongue protrusions and rhythmic body slapping to accompany a loud chant.

Today, haka are still used during Māori ceremonies and celebrations to honour guests and show the importance of the occasion. This includes family events, like birthdays and weddings.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.newzealand.com/us/feature/haka/&ved=2ahUKEwjr6feq14nhAhXHIDQIHV95DgIQFjAiegQIBxAB&usg=AOvVaw0P26mvdtxoVqL8_mbJm7eR&cshid=1552843206352

New Zealand's premier rugby team that re-introduced and popularized the haka before each of their matches. They are truly a thing of beauty and ferocity at the same time. If I were on the opposing team I think I'd consider another sport.

to shame racist Islamaphobe Ambassador Scottie Brown.

If I was the Prime Minister I would tell Scottie that since his boss foments so much racism, hate and Islamaphobia around the world with his hate speech, Brown will be sent home for agreeing with Trump this morning that the terrorist attacks had nothing to do with Trump although Trump was named by the terrorist.

but then there are probably some white nationalists who really are dumb enough to tell native Maori to get out of New Zealand.

OK, yeah, I know Maoris have these war dances where they stomp around and stick their tongues out in a effort to frighten their enemies.
Been there, seen that.

WTF does this even remotely have to do with the mass murder in Christchurch?

It is pretty cool. Those that died did not know they were warriors. But they were made to be warriors in those moments. It was a very respectful thing for them to do.