My favorite move there when someone points out thing that contradict is to say, "Yes. That's what you were told." Imply there's something mysterious to uncover about why those facts don't gel.
Alternatively: "I'm giving you the real history. That's not what your character knows to be true!"
My favorite move there when someone points out thing that contradict is to say, "Yes. That's what you were told." Imply there's something mysterious to uncover about why those facts don't gel.