Protesters denounced the blatant hypocrisy of the New Zealand government’s decision to designate Hamas as a terrorist organisation, while supporting Israel’s genocidal slaughter in Gaza.
Because you seem to be arguing from a ridiculous assumption that the government is more representative of people from New Zealand in general than the people protesting its support for a genocidal apartheid regime.
Fun fact: while the rest of the people get to choose which of the options to vote for, they don't get to choose the options. Besides, it's not like the majority of the people elected to the NZ government ran on a platform of "let's help good ol' Bibi commit genocide.
Unconditional support for the Israeli government is one of the many things most Western governments do against the will of the majority of the people to not get on the bad side of the US global hegemony.
Like when the countries go to war, the people don't get a say. It's not how democracy is supposed to work, but that's how it is right now.
There's a shitload of room between "dictatorship" and "everything the government does is perfectly in line with what the majority of the people want them to do."
This is clearly an example of the government not being perfectly representative while also not being a dictatorship.
That IS the main method to express that you're not satisfied with the actions of those more powerful than yourself, yes.
Edit: and also because 60% said so back in November and there's absolutely no reason to believe that the percentage would have decreased since then rather than the opposite.