Voltaire's god is the survivor-god from the myriad tried, tested and cast aside gods. Who is this god? Voltaire has the answer. He is a needful invention, and must be left at that. Look too closely and mankind and its fragile civility falls apart.
The Western world is largely the product of the Jewish belief system and its writings both Old and New Testaments. Much of our legal system and sense of justice comes from the pages of the Bible such as the rules against murder, adultery, assault, theft and proportionate retribution.
But far more than the basis of our law is the principle which states we are made in God's image. As such we have rights which the American Constitution describes as "self-evident". Edmund Burke, the father of conservatism, calls it the "natural law" which is embedded and not open to being legislated away. Thus, as people made in God's image, we have inherent worth and dignity which must be respected by government.
The Christian faith is therefore the restraint against arbitrary government which has a tendency to limit human rights and especially the freedom of speech and conscience.