Myth:
Christianity acknowledges the universality of human sin in addition to the universality of dignity. Therefore the Christian recognizes the limits of government because of the limitations of the (fallen) people who make up the government. The ultimate arbiter is God, not man the Scientist.
Response:
The idea of a limited government which not only has limited authority over the people, but which is also answerable to the people, is important in American politics. The American colonies broke away from England in part due to complaints over a lack of representation in a government that was itself insufficiently limited in power. What this myth is trying to claim, however, is that the very idea of a limited government is somehow dependent upon Christian principles. This is an absurd notion.
It's curious that this myth would presume to announce what "the Christian" recognizes and thinks about government, as if there were a single "Christian" position on anything — much less anything political. Christians have lived with, lived under, and led governments of every conceivable type — and more have probably done so with governments other than democracies that were not very limited.
Many important Christian leaders throughout history have not only not advocated limited government, but have in fact been very authoritarian. Did Luther or Calvin ever promote limited government alongside their treatises on sin? How many popes lived and died before the Vatican agreed that limited government might be a good thing after all — contrary to the Vatican's own history of absolutist rule over territories throughout the Italian peninsula?
We don't even have to look back in history to find Christians failing to support limited government — we need only look more closely at Christians in modern America who support the arguments from Bush advisors that the American president's power is virtually unlimited. How many conservative, evangelical Christians support Bush's claim that he can designate even American citizens as "enemy combatants" and thus deprive them of lawyers and trials? How many support the claim that the president can spy on Americans without court oversight? How many support the claim that the president can add "signing statements" to laws which assert which parts of the law the president will obey and which he won't?
None of this is compatible with the ideal of "limited government," but many conservative, evangelical Christians give unwavering support to it all — despite the claim in the above myth that their acknowledgment of sin entails support for limited government. There is nothing about Christianity which requires, prefers, or even implies the goodness of governments that are limited; on the contrary there is much in Christian tradition and history which is more supportive of authoritarian government.
It's certainly possible to argue that a recognition of human sin entails limiting the power of any human over others, but it's equally possible to argue that God will not allow his representatives or human government to go too far astray. Besides, how many conservative Christians really believe the first argument? If they did, they'd have to apply it broadly — not just in the context of human government, but all human activities including economics. I can't remember the last time I saw or heard conservative evangelical Christians arguing against free market capitalism and in favor of placing limitations on how much economic or market power any one person could wield.
What the above myth states might sound very natural for an American Christian living during this period of time, but it's not inherent to Christianity itself. Unfortunately, it's all too common for American Christians to assume that whatever they think, feel, and do is a natural part of Christianity itself — many just don't recognize how many of their beliefs, attitudes, and habits are shaped by American culture independent of their Christianity, or how their Christianity has been shaped by non-Christian cultural elements.
Christians living in America today are able to blend their political beliefs in democracy, limited government, equality, etc. with their Christian beliefs — and such a blending is obviously not too difficult, however many potential contradictions there may be. The fact that they can be blended is not a sign that they are in any way dependent upon each other, though. Christians in other times and places have found it similarly easy to blend their religious beliefs with completely different political ideologies: fascist, totalitarian, authoritarian, monarchist, etc.

