Unfortunately, there’s a small group of people who think becoming a republic with our own head of states means that New Zealand would “get rid” of the Treaty, te Tiriti o Waitangi, or void our founding document. This isn’t the case.
For years, supporters of the monarchy have claimed that the Queen represents a significant constitutional check on our politicians and is politically neutral. The British Prime Minister Boris Johnson's request to the Queen to prorogue (essentially suspend) parliament for a period, whatever your thoughts are on Brexit, highlighted this contradictory claim. If there's anyone who should not be surprised at the anger being directed at the Queen for her decision to follow hundreds of years of constitutional conventions, it should be those supporters.