Sometimes we share with others our sense of anger and outrage on matters that we are not directly related to. This practice is often thought of as a way to be prophetic and/or bring about change. It also has a "martyring" effect in that it could bring harm to the one expressing outrage (such as one expressing outrage over Presidents Trump or Obama may feel like they are "taking one for the team"). However, there is some evidence to suggest this action is self-serving. Here is the opening lines from the study:
When people publicly rage about perceived injustices that don't affect them personally, we tend to assume this expression is rooted in altruism—a "disinterested and selfless concern for the well-being of others." But new research suggests that professing such third-party concern—what social scientists refer to as "moral outrage"—is often a function of self-interest, wielded to assuage feelings of personal culpability for societal harms or reinforce (to the self and others) one's own status as a Very Good Person. (http://reason.com/blog/2017/03/01/moral-outrage-is-self-serving)
The article goes on to talk about this in depth, but the part I want to highlight is how to listen to outrage.
Often we listen to outrage of others with a desire to let the other person know we understand. One way we do this is by taking on some of their outrage. This "taking on" aspect of emotions of another person is over-functioning and inserting yourself into the center of the story of another. When someone inserts themselves into the center of my outrage, then I am quick to let that person carry my outrage for me. Meaning, that I will outsource my outrage to anyone who will be willing to carry it for me so that I don't have to deal with it.
Listening to the outrage of another means that you are willing to let them own their emotions and give them the space to do the work that is needed to learn from the emotions. If we take the work that is theirs to do, then we are stunting another in their maturation.
When we listen to outrage, it is important to remember that the emotions of the one outraged are their own feelings and you don't have to own them. When we take on the rage of another then we cannot deal with our own emotional lives - thus stunting our own maturation.