Chuck Todd made a deeply insightful point, noting that Barack "spent more time trying to impress Warren (or to put another away) not offend Warren," in contrast to McCain, who "seemingly ignored Warren and decided he was talking to folks watching on TV."
Warren may come away from this experience liking Obama more and respecting the fact that he seemed to take pains to not offend him and respect their disagreements. But I'm betting that if a focus group of undecided voters were watching this, they'd come away having a clearer understanding of McCain's beliefs.
It strikes me that this behavior is characteristic of Barack, at least in my experience with him. He's reluctant to confront the people in front of him, especially when he obviously would disagree with them. In a sense, this is a stereotypically (just stereotypically!) feminine quality -- don't you know someone like this? -- of one who goes to great lengths to avoid interpersonal unpleasantness with the people they're speaking with, and seems almost apologetic when disagreement is unavoidable.
This characteristic of Barack's may make him seem like a super-nice guy -- but is this really an attribute we want in a President? If the person running my country is going to have to sit down face to face with Putin or other enemies, I don't particularly care that he takes "pains not to offen him and respect their disagreements."
I want a guy who's going to leave our adversaries with a clear -- crystal! -- understanding of America's position, even if it means interpersonal unpleasantness will be involved. From misunderstandings about resolve or will or beliefs, foreign policy debacles -- and adversary overreaching -- too often springs.