Considering I can't prove a negative, are you able to prove a positive?
Because trust me, New Zealand's opposition parties, social media, and the real media, would be on that like flies on shit if there was even a hint that it had happened. All it would take is someone saying "Wtf, my FB post calling Jacinda Ardern a pretty communist was mysteriously deleted."
I guess it's good to live in a nation where corruption is low, and the rule of law applies to all, the media is free, and who deliberates on questions of law isn't decided by politicians.
Because I know that any of the behaviour you posit would be absolutely called out.
Like the time a New Zealand Prime Minister sent the Police in to find an investigative journalist's sources, because it embarrassed him and his government.
Or the time that the New Zealand Defence Force sicced the internal intelligence service on the same journalist to find his sources because he embarrassed them...
https://i.stuff.co.nz/national/politics/104638742/police-apo...
https://i.stuff.co.nz/opinion/130640313/the-dirty-politics-b...
The fact that a) these things happened concerns me but b) that it was exposed to the light heartens me.
So yeah, if you've got evidence of what you posit actually occurring, please share it.