I agree with this in the sense that conceptually, they aren't very different. Saying that you can write fic of a person if they're a character in someone else's fiction is indeed like saying "you can only do RPF of them if someone else did RPF first."
On the other hand, I can see it being useful for a rule - if a rule is needed - because it allows you to identify more clearly what's okay and what isn't.
Re: ars_belli
I agree with this in the sense that conceptually, they aren't very different. Saying that you can write fic of a person if they're a character in someone else's fiction is indeed like saying "you can only do RPF of them if someone else did RPF first."
On the other hand, I can see it being useful for a rule - if a rule is needed - because it allows you to identify more clearly what's okay and what isn't.