Separation of church and state is necessary because religion advocates faith over reason. The story of Abraham is a paradigm for this illogical and often amoral idea. Abraham was charged by God to sacrifice his son Isaac in order to prove his faith. Abraham was WILLING to do so. Isaac's death was fortunately avoided, but the tale begs the question: What would the faithful be willing to do in the name of their faith? It is highly irrational to sacrifice one's son based on one's faith. The answer is simple: the faithful would be willing to do anything within their power in the name of their faith. This includes but is not limited to: terrorism (think Scott Roeder), hate speech (think Westboro Baptists), and ostracism (just think). Now if that power were increased; say by electing one of these radical theists to a position of power, what would they be able to do? Let's examine the governments of faith:
Bloody Mary's Catholic government of England: 280 religious dissenters were burned at the stake
Spanish Inquisition: 3000-5000 executed; many heretics were tortured
Roman Inquisition: 1250 sentenced to death
Crusades (justified by theocratic Europe): 1,000,000 - 9,000,000 deaths
Thirty Years War (internal conflict between Catholics and Protestants): 3,000,000 - 11,500,000 dead
The list goes on and on. Theocratic governments characterized by making decisions off of faith instead of reason would be oppressive, genocidal, and amoral. I am not advocating an atheist state (although I certainly would like one), but a secular one. The separation of state from religion and the lack thereof will remove controversial issues and extremists from legal power. This is the necessity of the separation of church and state.
Based on this evidence and other evidence that you can find: "Would you or wouldn't you vote for Rick Perry?"