I understand Executive Privilege just fine.
But you obviously don't understand Washington politics.
Anyone Republican who refuses to answer questions or turn over documents is automatically guilty. This is all about what is going to happen in the media. The media doesn't care about Executive Privilege. They will hound the White House daily for the documents. Even without the documents, the headlines will all say "MIERS REFUSES TO ANSWER QUESTIONS ABOUT BUSH CRIMES".
They don't need no stinkin' documents to convict you in the media.
So, John Roberts also refused to turn over those same documents and he turned out "automatically guilty", hounded and eventually "convicted in the media"? Oh, no - that's right - he is currently the Chief Justice of the Supreme Court. I think I understand Washington politics just fine, thank you very much.