er, why would they?
It would basically be like a civil war in the case of the Baku vs. the Son'a, which the Federation frowns on getting involved in.(remember Picard's "blood feud" comment?)
And why would the UFP offer protection to the Baku when they would benefit much more greatly from the Son'a removing them? Especially since the Baku have nothing to offer the UFP.
Because good people don't only help those they can profit from.
But helping the Ba'ku with what even Picard calls a blood feud violates the Prime Directive every bit as much as interfering with a primitive society would.
Once again, you can't pick and choose how to apply a rule on a case-by-case basis. Either the Federation is forbidden from interfering in a society's internal affairs or their not.
Which is it going to be?
Except from it's very concept, the Prime Directive has been selectively applied. Some times I think it's just a dubiously worded Machiavellian scheme to give the Federation the moral high ground in any given conflict they chose to or not to get involved in.