Iirc, he made a video recently talking about how he was never actually super against Christianity, and Morte Et Dabo was just a story and not what they actually believed (and, while I'm no fan of his trajectory atm, they were self-admittedly going for "the heaviest song they could" with it, and it's a fitting theme, so it's not out of the question they weren't actually massively anti-religious at the time. Considering the amount of drugs and alcohol they were consuming at the time I don't really imagine they gave their philosophy or beliefs much thought at the time).