Protecting the "Fundamental Interest of the Presidency?"

Found an interesting letter from the President's hired gun, Fred Fielding. In it he asserts that the President is acting out of good faith and trying to protect a

...fundamental interest of the Presidency: the necessity that a President receive candid advice from his advisors and that those advisors be able to communicate freely and openly with the President, with each other, and with others inside and outside the Executive Branch.

But this really just cements for me the suspicion that the President has great heaping piles of manure to hide under his fancy oval office carpeting he had his wife design for him.

If he really had nothing to fear about what they would say, he would let them testify on the record. It appears to me that the President is hiding behind "executive privilege" not to save the presidency, but to save his own shiny white ass that most can see through his new clothes.