I would imagine if some things became known now, there would be such an uproar that it would threaten the functioning of the government. IOW, you know how everything stopped when the Republicans went after Clinton? The Congress barely functioned and Clinton could barely function as President.

We don't need that kind of crisis right now where the Dems go after Cheney and crew for what they did. That would dominate the news (news people have one-track minds) and the attention of the Congress. What would happen to the health care and other things Obama is doing? They would slow way down or maybe stop altogether while Congress started hearings after hearings after hearings.

The Pres. is being pragmatic.