Exactly. Under ideal conditions (and yes, the conditions in INS were not ideal), if Our Heroes primary concern was the Prime Directive (and that's a big if under the circumstances) they would have stood (standed?) down and withdrawn from the planet as soon as they became aware of the relationship between the Son'a and the Baku, for the same reasons they withdrew from Klingon space in "Redemption".
Well you said it yourself that conditions in INS were not ideal so what would you have the characters do let the Son'a kill them?
Because I don't see how standing down was possible or would have worked.