wow, i strongly disagree with your premise... by which i mean:
>no matter the cost
i can't imagine any culture that ever considered "destruction of the human race" an acceptable cost for anything. all good philosophy is inherently utilitarian; that is to say, one ought to have the greatest possible ratio of good to bad. the destruction of the human race negates all good, meaning that the ratio becomes 0/bad, where bad is a quantity of bad expressed by the untimely deaths of 6 billion people and everything they ever loved. it is the worst conceivable outcome, and therefore the epitome of evil.