An analysis of emotion The whole enterprise of categorization of emotions as this that or the other is problematic because there are just far too many exceptions.
As in the Nussbaum quote about anger being the source of payback or wanting to see someone get their comeuppance really sounds more like vengeance. The purpose of law is to exclude emotion from the equation and to offer fairness, which might equate to payback in some form. We consider a good judge to be a tempered one, not one that is fiery and spewing venom. In fact, we'd exclude a potential juror from hearing a case if he expressed hostility. On the other end of the spectrum, we have the sociopathic who can with a calm heart and cold blood commit all sorts of heinous acts, not motivated at all by anger, but simply carrying out their will.
And I'd think that anger is a very good thing in certain contexts, not leading to vengeance, but leading to something productive. The anger over injustice has led plenty to pass laws and start humanitarian organizations for example. Passions can be channeled to good or bad, whether the passion be love, hate, anger or whatever.
It just seems that Nussbaum is criticizing vengeance, which is hardly controversial, although to what extent this tramples on Kant's just desserts is another issue. That is to say, if the justification for giving you your just dessert is out of a respect for your autonomy and choice, then we've arrived at an alternative explanation than simply saying that we're punishing you because we're good and pissed off about it.
I see emotion as just that which moves you to action, thus the root "motion" within it. If we were emotionless we'd be as computers waiting for someone to offer a use for us. And so I'd submit that if anger over injustice moves us to feed the hungry, then it is a good thing, and if love of our country moves us to open fire into a crowd, it is a bad thing.
Catagories schmatagories.