It matters not a jot whether Bach, Michaelangelo or Milton were Christians. It mattered not a jot whether Einstein believed in God. What I said mattered was in the post that Brendan is taking such exception to:

If your imagination, creativity and poetry are driven, or significantly influenced, by your religion, then 'tis you who has the closed mind. Your imagination is severely ringfenced. You won't be able to see past a perverted view of the world and the universe, with all its diversity and beauty staring you in the face, purportedly created by a rather abject, inexplicable being. That is false and it can't help but close off that part of your mind that should be free to contemplate nature as the source of edification through joy - and knowledge.

It would be very arrogant indeed to assume that the artistry of Bach, Michaelangelo and Milton were driven, or significantly influenced by, their religion. I should like to know how you can possibly know that. On the contrary, it is well known (excuse weasel words there...) that, for example, many great composers wrote their most cheerful works when they were often struggling with things going wrong in their lives. Mozart wrote The Magic Flute in the final year of his life, when he was burdened with financial worries and poor health. Beethoven wrote some of his most sublime pieces, the supremely lyrical and upbeat quartets in E flat and C sharp minor for example, and the witty Diabelli Variations, after he had completely lost his hearing and was ground down with distressing and chaotic circumstances in his private life. Great artists are well able to stand outside themselves. Whether Beethoven believed in God or not is a moot point, yet he wrote the amazing Missa Solemnis. Shimrod is correct in saying that these men were not solely (if at all, I'd add) talented as a result of their faith. He could easily have added that it's perfectly possible to deliver oneself of great art in spite of faith. And why not.