The same applies to many ideas that build upon other concepts being the case. You could probably make an argument that no ideas at all are wholly independent facts in the sense that they do not depend on the truth value of other ideas. Often you can skip dealing with a large swath of ideas simply by rejecting some upstream idea they all rely upon.

Religion, in this case, was a good example. That, and there's always some chance of hearing something interesting about holy underwear.