For those curious, he started writing Swamp Thing in the 1980s and he was kicked off the book because he was going to have Swamp Thing meet Jesus.
Just to clarify, that particular storyline was conceived by Rick Veitch, who was Moore's successor on Swamp Thing. Veitch resigned when DC management decided not to run the story. This was around the time of The Last Temptation of Christ, and DC didn't want to attract the ire of fundamentalists.
For deity-invoking cosmological madness from Moore, himself, give Promethea a whirl. Anyone with any interest in occult philosophy (Kabbalah, Hermeticism, Zen, etc.) should love it. For anyone else, the art (by J.H. Williams III & Mick Gray) may be the primary draw, the 32 issues together comprising a visual tour de force. Highly recommended.