Once again; where is the RULE?
A proper noun is the name of a specific person, place or thing. Proper nouns are always capitalized. That is the rule. There is no exception for God or the Bible.
To treat a proper noun as a common noun is a sign of disrespect. I do that with words like muslim, islam, or obama; sometimes even at the beginning of a sentence, just to make it clear the disrespect is intentional.
I’m no expert in grammar. If someone who is wants to pick my posts apart, they could have a field day. Proper nouns are a pretty simple concept though. The rule of capitalizing proper nouns used to be known to all children by the time they finished elementary school. I don’t know what they’re learning these days, but I’m sure proper nouns are still to be capitalized, whether the children know it or not.