Humans throughout the millennia have painstakingly created governments, laws, and social structures—collectively known as civilization—to protect us from ourselves. Once in a while a doofus like Rousseau emerges, too clever by half, arguing that civilization has corrupted humankind. Would we be better off without it, living in our pristine state of nature? No, Hobbes had it right: the life of man in a state of nature would be “solitary, poor, nasty, brutish, and short.” You'd be better served with a sober view of the human condition and come to the realization that we humans need to be governed. Bob Dylan, during his Christian phase, had it right in his song Gotta Serve Somebody: "It may be the devil or it may be the Lord, But you're gonna have to serve somebody."
It's vital that governments appreciate the depraved side of humankind, but sometimes regimes use this knowledge for their own nefarious purposes. A classic case of a pessimistic view of human nature leading to oppressive government is the first Chinese empire about 200 BC or so. The emperor Q'in Shuang-di governed by means of a political ideology that historians today call Legalism. Legalists in this sense were those thinkers who had a negative view of human nature and concluded that government must be heavy-handed to put them in their place. It emphasized negative, not positive reinforcements. (The term "legalist" refers to the idea that rulers could change the laws if need be, and not slavishly adhere to tradition. So if the laws aren't working to keep the people in check, a ruler can change them.)
It's vital that governments appreciate the depraved side of humankind, but sometimes regimes use this knowledge for their own nefarious purposes. A classic case of a pessimistic view of human nature leading to oppressive government is the first Chinese empire about 200 BC or so. The emperor Q'in Shuang-di governed by means of a political ideology that historians today call Legalism. Legalists in this sense were those thinkers who had a negative view of human nature and concluded that government must be heavy-handed to put them in their place. It emphasized negative, not positive reinforcements. (The term "legalist" refers to the idea that rulers could change the laws if need be, and not slavishly adhere to tradition. So if the laws aren't working to keep the people in check, a ruler can change them.)
However, just because one embraces a pessimistic, or at least negative, view of human nature doesn't necessarily mean that one will support an oppressive, authoritarian government. Some of our own founding fathers, for instance, had a rather dim view of human nature. Men like James Madison and John Adams advocated liberty and independence from Britain, but at the same time they were suspicious of "man," and tried to construct a system that accounts for human foibles.