Well, first up, I am a New Zealander and citizen of Australia, so I do appreciate my in-depth analysis, thanks.
Secondly, the arrival of the British decimated the indigenous cultures, across the planet- they will never be what they were. Some of the culture remains, yes, but there is no such thing as benign interference- the moment two cultures meet, both will be changed, forever.
So, instead of allowing humans to invent the warp drive, the Vulcans should have just come down and GIVEN it to us? Is that benign interference? Should they then have said: "Y'know, this emotions thing you got going on, you know what's better than that? Logic!" Because, y'know, they are the superior culture, so we should do things their way. Or maybe we should be allowed to do things our way- maybe in doing so, we'd actually have a unique understanding of the universe, invent things the Vulcans would never have thought of, have a unique culture. And it's not the Federation's place to override the imperatives of other cultures- and they don't have a choice in the matter. If you show up on a planet and introduce them to the concept of a phaser their world will be changed FOREVER, whether you want it to or not, it will- it's not a choice, it's just a thing that will happen. The PD is designed to prevent this. There is no benign interference.