Starfleet believes that if a species is going to make a mistake or get wiped out by a natural event or evolutionary trait, that is what was suppose to happen. Why interfere in the natural course of events? Messing with it could lead to greater problems. Even the ENT episode that introduces Starfleet to the concept is one of the Enterprise being able to save a species with a genetic defect that will eventually end their species, but not doing so as it would prevent the natural course of evolution on that planet as the next species would be able to become dominate as the other species dies out.
It seemed like S.F took a turn into some weird pseudo scientific logic.
The logic could be flipped, why should 22th-24th century humans fight any lethal, contagious disease that threatens them, since it could be interpreted that it was natural selection in progress?
There was an example where Picard was trying hard to prevent a moon from falling out of orbit, as it would cause massive devastation and destruction for that planet's world.
The logic could be used, by a Q for example, is that it was meant to happen to a lesser species that couldn't prevent it themselves. So they wouldn't bother helping even though they could with a snap of the finger.
@Nightdiamond: The zero-tolerance policy arguably has upsides for episodic TV - it facilitates disguising-as-natives plots, and provides easy drama with the risk of discovery. But yeah, it definitely has some pretty glaring moral downsides.
Now, it might have been extremely awkward had Vulcans made contact in, say, 1938, and argued against starting a new World War - how could they prove who they were to the world as a whole without freaking entire countries the heck out? Now that high-quality planet-wide communication is widespread and cheap, however, not to mention we've had decades of sci-fi scenarios to think about such things, I think we'd be pretty ready to make limited, diplomatic-only contact with a race like Vulcans today, even without Cochrane's warp engine.
True, and it seems like Starfleet has a somewhat hypersensitive attitude toward the idea of contamination.
It seems that S.F feels that even a slight, friendly, non evasive gesture towards a 'lesser' culture is dangerous, and will result in catastrophe.
It's almost like the pacifist concept. Pacifism is an advance, honorable philosophy, but taken to an extreme, it becomes almost illogical.
For example, a power or planet that refuses to protect themselves even to save their own lives or protect the freedom of themselves and countrymen.
I can see the wisdom of not contacting very primitive, superstitious cultures.
But what harm could there be to contacting a culture that has reasonable knowledge of science and space?