Thank you, Cap'n T. I think.
Further to that, there would have to be some kind of threshold or "cut-off point" for the Prime Directive. Otherwise, the UFP would be unable to deal with ANYBODY - seen a few truly idiotic examples of this kind of PD misuse in Next Gen.
You are not supposed to interfere with a primitive / developing culture. Fair enough. Not even if they happen to sitting on stuff you want. Definitely Fair Enough. If one of the natives gets lucky enough to spear a member of your Away Team, well, them's the breaks. Still hands off.
If the culture somehow figures out the existance of the UFP on its own and then institutes communications, that is probably where one set of rules should end and a new set begins. Consider sending in the diplomats.
If the culture demonstrates both the capability and the willingness to deliberately endanger the UFP, its allies and portions thereof .... yeah, that is a biggie. Shooting down Federation starships should definitely fall into that general category. Ain't necessarily developing
, more like well and truly developed
Also consider that, in certain 'crazy computer' scenarios ('The Apple', 'Return Of The Archons', 'Spock's Brain') whilst the subjects of the CC were primitive, naive and (mostly) harmless; the things controlling their fates and generally running their worlds from behind the scenes were anything but. Applying the PD to them could (IMO) be rather like extending full PD protection and privileges to the Romulans or Cardassians because of having conclaves or reservations of 'primitives' somewhere in their respective empires.
So, dude, you might consider laying off Kirk just a tad.