While the first may be true (I doubt if Sharpton actually pays very close attention to his opponents stump speeches, and he doesn't have much of a staff to follow these things, so its plausible, but you seem certain that it isn't so no more discussion is warranted there), even having heard the comment before does not preclude a genuine angry response.  Which is what I have been arguing; the chances are just as likely that the comment did (or had all along) made Edwards angry.  It was pretty clear from his response (at least over the radio, which is where I heard the debate)that he was actually angry.  

Did he use it for political gain?  Without a doubt, but I can't say for certain (as you appear able to do) that the whole thing was simply a ploy or an "attack". The anger could have been and certainly seemed to be genuine.  And it did not appear to be a canned response (otherwise he would have come up with a better one I have to assume; the guy's not stupid).  You appear to disagree and find that the only reasonable explanation is to smear Dean, or to pander.  You seem unwilling to even admit, grudgingly, that there could be anger there.  That the original comment from Dean could insult.  I'm only saying that in interpreting the event as such, there's a lot of other information that goes by the wayside, and that information is actually pretty useful.

There's a certainty around here that is so easily reinforced because so many people see things the same way.  That makes for a "self-evident" nature to things that aren't always as self-evident when you step away from the shared vision.  If I'm cranky, its because trying to explain this over and over again to the conventional field of vision around here has worn me down.  I don't have as much patience or a sense of humor about it as I used to, I will admit.  

I personally find that kind of certainty dangerous, so I will always challenge it, sometimes not so wisely.  Obviously many people take comfort in it.  I'm not going to argue with you about what is "obvious" because nearly everything you've described as obvious I can see a plausible and credible alternative explanation for.  It may not be true, that explanation, but it is certainly plausible and credible.  On the other hand, your obvious explanation may not be true either.