There's always a presumption of innocence as far as the justice system goes. He doesn't have to prove that he's innocent (by signing keys, etc.), someone else has to prove him guilty with actual conclusive evidence -- something that can't be done until the real Satoshi steps up and proves his identity, thereby invalidating CSW's claim.
Your line of think makes absolute no sense at all.
Nobody is accusing him of saying he is satoshi. He is deliberately saying that, and that's a crime by itself. Maybe he can try to defend himself with your line of thinking, but he must prove: he is the one claiming and trying to make money of this claim.
you cannot pretend to be someone else, it is a crime. If I do an interview on tv saying that I am some other guy , that's a crime everywhere in the civilized world. He is doing that to manipulate markets and make money, which is another crime.