There is an article in the NY Times about the French humanist Diderot. He was a great champion of free thought and a great critic of the church.
If I taught at a seminary I would have a entire semester dedicated to thinkers who were enemies of Christianity, but also great friends to humankind. Respectfully reading people like Voltaire and Diderot are like radiation treatments for the cancer of bad religion. For example, Diderot is often quoted as having said, although its source is open to question:
“Humankind will never be free until the last king is strangled with the entrails of the last priest.”
While I, as a preacher, have no wish to be strangled with a politician’s small intestines, I can hear the frustration born of a love of humanity behind these words. I obviously disagree with Diderot, or whoever said this, that religion is always unhealthy, but the saying is absolutely correct in one sense. The twin bullies of church and state have caused untold suffering to humankind. If I go into politics or the clergy, I must do so to serve not to tell people what to think or do.
I would not hold to a faith that hides from its critics, but have much trust in a faith which is eager to pass through their purifying fire. True faith feels no need to refute its critics, only to learn from and transcend them. It is not true faith if it cannot bath like a dragon in the harshest acids of truth.
http://www.nytimes.com/2013/01/25/opinion/diderot-an-american-exemplar-bien-sur.html?_r=0