I don't think it's that he knows to much it's just that he doesn't want to fire a fellow Muslim.
I do think he knows too much. Who would you pick to gather intelligence if you wanted to overthrow the country. The head of the CIA would be my choice. I think he is the only one who has access to all the information and plans at this point and losing him would be catastrophic to Obama's plans.
There is danger from all men. The only maxim of a free government ought to be to trust no man living with power to endanger the public liberty.
Public virtue cannot exist in a nation without private, and public virtue is the only foundation of republics. There must be a positive passion for the public good, the public interest, honour, power and glory, established in the minds of the people, or there can be no republican government, nor any real liberty: and this public passion must be superior to all private passions. John Adams