That will only work if the atheist doesn’t have any patients proficiencies, which comes with almost every athiest subclass. This gives the athiest advantage on charisma, intelligence, and wisdom saving throws from a character with the Christian class against the atheist. This is of course negated completely if the christian comes into the battle with the lawyered-up buff, but I didn’t splurge on the LegalEagle’s Book of Many Laws. So I’m not sure how that mechanic works.