—Liberals believe humans are perfectable with the right set if laws and programs.—
Rousseau teaches us that human beings were essentially vice-free when they were primitive hunter-gatherers. What we call human nature, original sin, or what-have-you began to manifest itself when human beings became civilized roughly 10,000 years ago. NO civilization, whether laissez-faire capitalist, totalitarian, or social-democrat can perfect human beings as it is the nature of civilization (all civilizations in all places) which brings out the “badness” in mankind. Since few people wish to return to a lifestyle where we men would don animal skins and hunt large-game over the tundra while the women gathered roots and berries, we are stuck with human nature (or, if you are an Augustinian, “original sin”).
Rousseau did more damage to Western Civilization than the Islamic empire ever did.