You don't see a difference between me knowing who you have associated with and you not telling me who you associated with ? Its like me having witnesses that you robbed a bank and you saying "What bank ? "
Not when the government comes out and plainly states that they do not. If I can paraphrase accurately Wolfowitz says: "Clearly he has associates, but he won't tell us who they are."
If they had any credible information whatsoever, they wouldn't need his cooperation to build a case. Furthermore the constitution protects his right to refrain from cooperating. It is absurd to suggest that one accused of a crime (and in this case he isn't even charged with a crime) must cooperate with the authorities or be assumed guilty. That turns our alleged justice system on its ear.