Crawford asked Barr whether he agreed with Mueller's "interpretation" that he couldn't make a decision regarding obstruction--after laying out 11 instances of "possible" obstruction.
Barr: "I personally felt he could've reached a decision ... he could've reached a conclusion."
"The opinion says you cannot indict a president while he is in office, but he could've reached a decision as to whether it was criminal activity. But he had his reasons for not doing it, which he explained and I am not going to, you know, argue about those reasons.
"But, when he didn't make a decision the Deputy Attorney General, Rod Rosenstein, and I felt it was necessary for us, as the heads of the Department, to reach that decision."
Crawford then stated that Mueller "seemed to suggest that there was another venue for this, and that was Congress."
Barr: "Well, I don't know what he was suggesting, but the Department of Justice doesn't use our powers of investigating crimes as an adjunct to Congress."
And that was that. I think Barr played this smartly. He gave Crawford a full response, but deftly declined to get down in the gutter with Mueller. Why should he demean himself by treating Mueller as a respectable interlocutor, or even as an equal? If Mueller wants to rehabilitate himself in respectable circles of government legal service he'll have to do it on his own.
On the other hand, in typically understated but direct fashion Barr makes clear his view of Mueller's reprehensible performance for anyone who cares to consider his words:
... the Department of Justice doesn't use our powers of investigating crimes as an adjunct to Congress."
But Mueller did. It's a slap, but a principled one, without being petty. Mueller as Special Counsel was a political actor by his own choosing, and Barr has nothing but contempt for him.
BONUS: Michael Goodwin also captures the reprehensible smallness of Mueller well: America left to face the nasty consequences of Robert Mueller’s actions.
UPDATE: I just found a longer video of the interview in which Barr is asked whether he believes, as President Trump has said, that Obama officials committed treason. Barr responded, "Not as a legal matter." In other words, not as "treason" is technically defined in the Constitution, Article III, Section 3:
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort.
Here are those remarks:
President Trump thinks some committed treason.
Crawford: "You don't think they committed treason?
Barr: "Not as a legal matter, no."
Crawford: "But you have concerns about how they conducted the investigation."
Barr: "Yes, but, you know, sometimes people can convince themselves that what they're doing is in the higher interest and better good. They don't realize that what they're doing is really antithetical to the democratic system that we have."
That sounds rather like Jack Goldsmith, who sees "national security bureaucrats who use secretly collected information to shape or curb the actions of elected officials ... as a vital check on the law-breaking or authoritarian or otherwise illegitimate tendencies of democratically elected officials.