Human Nature, the Role of Government, and Original Sin

There is a fundamental disagreement in our nation today about the role of government. This disagreement, at its core, is between two positions in complete opposition and contradiction to one another. What the two positions believe about human nature is important:

Utopian Progressivism's Faith in Human Nature: a conviction that at least some human beings, and thus human governmental structures, possess a limitless capacity to do good. Erica Payne is the archetype of this philosophy, vide:

The government of the United States has millions of employees, offices around the world and a budget of $3 trillion dollars. It is the single most powerful entity in the world. It can ensure freedom, protect the weak, explore new worlds, create industries, transform economies, cure disease, spread prosperity, re-build war-torn nations and even reach the moon. If we can change the leadership of that government, we can change the world. 

The Practical Progressive, p. 21

Democratic Capitalism's Pessimism About Human Nature: a conviction that all human beings, and thus human governmental structures, possess a limitless capacity to do evil. Michael Novak explains:

The system of democratic capitalism, believing itself to be the natural system of liberty and the system which, so far in history, is best designed to meet the premises of original sin, is designed against tyranny. Its chief aim is to fragment and to check power, but not to repress sin. 

The Spirit of Democratic Capitalism, p. 310

How should we then deal with the conflict between these two views? We are careening down the utopian path, towards a world in which, as Novak puts it, power will no longer be fragmented and checked. Instead, the nearly unlimited capacity for unitary, unfragmented government to do evil will be allowed to reign without restraint.