Two Presidential Power Questions for Ben

Ben is shocked (shocked!) by Harold Koh's invocation of indefeasible presidential powers in his Oxford Union speech.  But insofar as Ben is implicitly accusing the former Legal Adviser to the State Department of hypocrisy merely for having the temerity to suggest that such powers exist, I wonder how he'd respond to the following two questions:

1. Would you take seriously anyone who denied the existence of any and all indefeasible presidential power (and who would, therefore, think that Congress did have the power to enact the Command of the Army Act of 1867, which effectively made Ulysses S. Grant, rather than Andrew Johnson, Commander-in-Chief of the military)? 
2. If not, can't we accept that some claims to indefeasible presidential powers are stronger than others, and that prosecutorial discretion and control over diplomatic relations might raise slightly different cases as compared to statutory bans on, for example, torture?

Reasonable folks can certainly disagree about whether there are inconsistencies between positions taken by Professor Koh and those taken by Legal Adviser Koh (as Justice Jackson put it in Youngstown, "It even seems that President Taft cancels out Professor Taft"). But it seems to me to be caricaturing Koh's views to a degree that's just not helpful to imply that the mere invocation of the idea of indefeasible Article II powers is hypocritical.