Arianna wants Obama to get angry. I've heard other people say this offline as well. I just don't buy it.
For one thing, anger would suggest that McCain has gotten under Obama's skin. A cool unflappability has been an Obama calling card for about a year now--throwing that out the window with two months to go doesn't strike me as such a hot idea. I also think he's as likely as not to get media coverage emphasizing not the righteousness but the rage, fueling a storyline that Democrats are in some kind of panicked meltdown.
Finally, we all know the sad but real stereotype of the angry black man, a trap Obama has brilliantly avoided. Just as Republicans are waging a culture war, I just don't think that's where he wants to go.
If there has to be righteousness, let it come from other quarters--respected party surrogates, perhaps like Al Gore. Better yet, maybe Obama can assemble, or put in a TV ad, a group of heavyweight corporate and civic leaders--Warren Buffett, Susan Eisenhower, the most senior ex-military man he can find (Colin Powell being the dream)--to implore Americans not to get distracted from the burning issues that really affect their lives.