The Overlord wrote:
Was humanity as certain to die as the Valakans were in this episode? Because this episode presents it as an almost certainty they will. If the Vulcans knew humanity would almost certainly die and did nothing to help, they would be psychopathic.
If you have seen Carbon Creek
you know that this is precisely what the Vulcans would have done hypothetically during the Cold War and have actually done during WWIII. They stood idly by while Earth was about to destroy itself in a nuclear armageddon.
The Cold War is not the same as a plague ravaging a population, the Cold War could have resulted in mass death, but didn't this plague did. As for WWIII. You are forgetting that the amount of effort Phlox and Archer had to put in to stop the plague was minimal compared the effort the Vulcans could have needed to stop WWIII.
Phlox and Archer got involved, they made the cure and then they decided not to give the cure, the broke the PD by getting involved in the first place. Heck the PD didn't even exist back then, so there was nothing really stopping them from getting involved in the first place. They fact they got involved, give the Valakans false hope and then decide not to give the cure to them. That comes off as extremely cruel and callous. As was mentioned before, this is like someone with a jug of water coming across a man dying of thirst and decides not give any of his water to the man and then says that was the moral thing to do.