This Joe Klein piece on Obama's passion (or lack thereof) has been getting some play in light of his choice of Scranton's finest. The gist of it is that Obama isn't showing his emotions, is too nuanced and cerebral (please browse 2000 and 2004 for the rest of the complaint).
But when you start talking about Obama needing to act more passionate, angrier and more outspoken, isn't the single most obvious guarantee from such a move that he'll be called out for acting like a preacher, and channeling Jesse and Al? The model of prominent black politicians is so narrow and so artificially dominated by those two men that it invariably draws comparisons - and has for much of Obama's candidacy. That's the problem with the "passion" argument in a nutshell. The more outspoken and outraged Obama acts, the closer he gets to a preexisting model into which he can be shoehorned.