>>16424797
It depends on what you mean by a christian policy. Since you're american, i assume you mean something like abortion. that isn't really a religious issue, even if one side of the debate has predominantly christian views and justifications. For example, if a senator proposed an increase in welfare spending and his personal reasoning is that he has a christian duty to help the poor, that would not be christian policy. Voters voting on non-religious topics with a religious worldview and ethics is not a case of the separation of church and state, that's just democracy at work.
But laws like "the state religion is x denomination of Christianity and everyone must convert" or "Christians can no longer attend mass on a Sunday" would fall under the separation of church and state. The formal separation is not having the church as part of the state, the substantive separation is secularism and a neutrality on religious matters.
This all springs from the English Civil War which was (in part) caused by division between Presbyterianism in Scotland and Anglicanism in England, and the religious policies of Charles I. The war had a major effect on both Hobbes and Locke, with the later writing his famous 'letter concerning toleration' which is the cornerstone of modern conceptions of secular government. So the initial intention was the preserve peace in a religiously divided polity by removing the state as an instrument to impose one view or the other.
In any case, people misinterpreting it has little to do with its importance in political thought.