Well said. Phasers in the hands of Khoms (and the Yangs who witnessed the incredible sight of "fireboxes" at work) alters the culture more than someone reading a native document, simply reiterating its meaning.
Prior contamination doesn't give you liberty to do anything you want. Kirk pushes an old man out of the way and gets his greasy paws all over a 2,000 year old document and starts waving it around. And Kirk DOESN'T simply reiterate it's meaning. He gives it a sweeping new definition by saying it applies to the Kohms as well.
If Kirk had just left: executions, looting, pillaging, raping (No, I'm not going to give the Yangs any more credit than any other conquering people)
After Kirk leaves: (In story) At the very least the Yang leader has promised vast social reform.
(In reality) As stated earlier in the thread, some sort of in-house struggle probably resulting in the deposing of Cloud William.
That is the definition of the PD *Interference*.