It does not matter what you believe. The right to fair use cannot be a priori. Not even First Amendment rights are a priori, they were learned through experience or in other words a posteriori.
Ah. You're arguing in the realm of philosopy, where I may or may not agree with you; I'll have to think that through.
I'm arguing in the realm of law. Perhaps to clarify, in my future use here, I'll simply use the term "prior" and not "a priori."