On Darwin being a Christian, see the PBS site where James Moore (Darwin's biographer) talks about the slow death of Darwin's faith. Darwin clearly had "issues" with the Christian God and worked them out via his theory.
What the page says is that in his later years, Darwin struggled with issues of religious faith. To some extent, this had to with the fact that his theory of natural selection refuted the view, popular among the Christian naturalists of his time, that the complex and sophisticated structure of creation showed that "divine design" had to be at work. But in fact, when Darwin set out on his famous voyage aboard the H.M.S. Beagle, he was himself a believer in "divine design"; he had even studied with one of that theory's leading proponents, the Rev. Adam Sedgwick (a geologist), in preparation for his trip. His observations on the trip caused him to question and ultimately reject "divine design," but he remained a strong proponent of Orthodox Christian morality. The real crisis of faith that turned Darwin away from Christianity was caused by the death of his 10-year-old daughter Annie in 1851. (This article in Newsweek also offers some interesting information on Darwin's scientific and religious beliefs.)
My statement that "Darwin was a Christian" oversimplified the complex reality of Darwin's views, and should have been more nuanced. However, the notion that Darwin developed his 'theory of natural selection as a way to "work out his issues with God" is preposterous, if only because he developed his theory more than a decade before he developed his "issues." It also says a great deal about the mindset of ID proponents, who treats scientific inquiry as essentially driven by ideology.
Incidentally, that is what makes ID a fundamentally non-scientific enterprise: not that it is driven by religion, but that it is driven by ideology. That is, its proponents question evolutionary theory not because they are dissatisfied with the scientific/factual evidence for it, but because they don't like its conclusions. To be sure, they look for and claim to find scientific and factual holes in the theory, but the main (or only) reason they start looking is that they don't want it to be true. It makes no difference whether a critique of Darwinian theory is motivated by defense of religion or, say, by concern that biological Darwinism easily lends itself to apologetics for social inequality. In both cases, the motivation is ideological, not scientific.
Are there people who champion Darwinian evolution because they dislike Christianity and religion in general? Yes, I'm sure there are. But there is simply no evidence that most scientists or most supproters of science are so motivated, and there are plenty who consider themselves religious.
More: See also this post for a funny, yet insightful, 1872 poem (originally in Russian, translated into English by yours truly) on the conflict -- or lack thereof -- between Darwinian theory and religion.