I don’t find the idea absurd at all. Unnecessary in these days - yes. Absurd - no.
Tradition dies hard, and it was not that many generations ago when all one had to go on was a person’s oath, and that oath only meant something if the person speaking it believed it too.
And, O’Donnell is wrong about “the government that invented the separation of church and state” - the concept as understood by the founding fathers was rooted in a Protestant doctrine that began as an anti-Papal sentiment.