The Single Biggest Mistake Each Star Trek Movie Has Made
5. Star Trek: Insurrection - Ignoring The Prime Directive
The Mistake: Either the Federation knowingly got themselves involved in a blood feud, or somebody did absolutely no background checks on the Son'a.
Why?: This is a pretty big issue, whichever way you look at it. In the first option, the Federation is well aware that the Son'a and the Baku are the same race. Therefore, they abandon the Prime Directive entirely. Involving themselves in the internal affairs of another world and people is strictly against everything they stand for. While the possibility to cure many illnesses is a tempting target, it is highly unlikely that Starfleet would sanction this.
So, let us now assume that Starfleet doesn't know the true origins of the Son'a. Admiral Dougherty says that the Prime Directive doesn't apply as the Baku aren't indigenous to the planet, besides which there are only 600 of them to move.
Who does the research on Starfleet new allies? Does everyone who knocks on the door get allowed into the Federation's inner circle? There is serious misstep in the checks on the Son'a, as a quick scan with a tricorder reveals their ancestry. Whichever way you look at it, Starfleet acts totally out of character in this film.