It’s kind of the downside of the “make your own reality” mindset.

“We believe in freedom of religion.”
“But if Christianity is favored won’t we just end up with a Christian nation?”
“Oh no, nobody has to be Christian. But it is true the Constitution only applies to a moral and religious people.”
“So we have to be a religious country? How about Islam? Hinduism?”
“Of course not. The Founders were Christians.”
“So we’re a Christian nation?”
“No, we believe in freedom of religion…”

[rinse and repeat]