Righteous indignation is an emotion we feel when we become angry over a perceived mistreatment, insult, or malice. It is akin to what is called the sense of injustice. Christian doctrine believes that righteous indignation is considered the only form of anger which is not sinful, e.g., when Jesus drove the money lenders out of the temple.
Dealing with righteous indignation, it is important to show the difference between this and the emotions of anger or impatience. It is difficult separate this emotion from anger, but few have been able to draw a satisfactory difference. The only difference between righteous indignation and real anger that can be drawn is in degree and not in quality.
The emotion of righteous indignation is the feeling excited by that which is unworthy or disgraceful; anger mingled with contempt, disgust, or abhorrence coupled with a sense of true superiority through believing in a personal conviction.
If you have it, you know it because you believe that your cause for anger is just. Use it wisely.