Tom Brokaw: Why was Biden laughing during a discussion of Iran's nuke program?

“I don’t think he was laughing,” said Brzezinski, but rather showed that he was “amused” at Ryan’s approach to these issues.

It’s about tone, Brokaw argued, regardless of one’s level of amusement, and he maintained that Biden’s demeanor should have been “dialed down” during discussion about critical, serious matters.