In regard to the oath of office you're mixing up preference with requirement, as the Bible is not required at all. Four Presidents have not used the Bible and when you get below Presidential level it becomes more common.
Plenty of examples of issues with a mixing of Church and State exist, but that's not one of them.
Q: Did the Supreme Court rule that it is illegal to take the oath of office with anything but the Bible? A: No. That is a made-up claim that originated on a self-described satirical website. FULL QUESTION Did the United States Supreme Court rule that Congress has to swear on the bible? FULL...
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