I know you say that forgiveness and justice should grow up together, but I still am not convinced.  Isn’t it the case that as I forgive and soften myself toward the one who injured me, I become less motivated to do the hard work of justice-seeking?  I say this because a little anger in the heart can toughen the heart to move forward with the quest for fairness.

You make a good point that mild and short-term anger can motivate a person to seek fairness.  Here is another perspective: As you forgive, you seek the good of the other person who hurt you.  Part of this seeking after the other’s good is to assist that person in growing to be a fair person.  So, the short-term anger is good for motivating the injured person to stand up for his rights.  The longer-term forgiving is good for motivating the injured person to help the other be fair for that other person’s sake.