Edit: There were more pages in the thread than I realized before posting... oops.
There's a very serious problem with the "Life is Sacred" rule:
There is at least one known alien race who procreate exclusively using the abandoned corpses of other species. Not to mention the many alien life forms whose continued existence requires them to kill other life forms (sometimes sentient ones, specifically).
The other rules don't help either. Who is Starfleet to decide what "harm" is, or whether a given result is worse than any other?
Suppose a non-sentient alien preys on sentient aliens who cannot defend themselves from it. Taking action to protect the sentient aliens will result in the death of the predator. Taking no action will result in the deaths of the sentient aliens. What's "worse"?
When it comes down to it, I think the Prime Directive is not a tool to further or encourage morality of any kind. It's more of a way for Starfleet to cover its own ass and avoid the entire Federation having to take responsibility for unforeseen consequences of individual officers sticking their noses where they don't belong.
One Starfleet captain inappropriately (according to the PD) granting asylum to one refugee and causing a war is bad enough. When you have millions of captains, your potential liability is exponentially greater.
