I've wondered if there were actually a righteous kind of anger. James is pretty clear that the anger of man doesn't accomplish what God considers righteousness (1.20). The counter to that is Jesus in the Temple, apparently with a strong amount of anger driving out the money changers with a whip (and I don't think it was a for show or just a deterrent).
I would offer that there are two questions to ask to see if any particular anger that you're feeling is righteous anger.
1. Is it the Truth/Right that is being offended or is it me?
This takes some discerning since I'm often on the side of "right" (as I see it, anyway). But if this had no personal effect on me, would it still warrant my ire? Is it the injustice of it or my personal preference or opinion that has been infringed upon? Like I said, some discerning is certainly needed.
2. Does the offense compel me toward a biblically modeled or biblically commanded action?
If the answer is no, then either (a) I'm not mad enough about it or (b) I'm just mad and it's not really righteous anger. Righteousness always seeks the reckoning and reconciling of things, the relational rightness (a.k.a. shalom) of the world.
If the answer is yes, then what can I do that is biblically modeled or biblically commanded - and can I do that in love? I can do a biblical thing without love, but I may end up being a clanging gong or a noisy cymbal (1 Cor. 13).
Righteous anger requires a pretty high bar, one not often reached by the normal situations in our normal lives. But it shouldn't simply be set aside.
But that's just me thinking thoughts...