We have a national epidemic going on. No, it usually doesn't kill people; it just has the potential to put them in abject slavery. It's called righteous indignation. Hey, this stance is as American as cherry pie; and less caloric. Therefore, it's something else to feel righteous about. The Puritans were definite promoters of righteous indignation with their view of things; but possibly the Native Americans had their own stimuli for righteous indignation.
Some examples of things that cause people to mount on their elevated equines are the persistence of Confederate flags, the team names of certain teams (like the Washington Rednecks), gay marriages, cheerleader costumes, the quality of television, what girls wear on the beach, and why we don't have nice things like a good domestic beer.
A psychologist should ask what's the reinforcement for this behavior? On a biochemical level, the brain uses reinforcement learning which is mediated by dopamine, Increasing the frequency of certain behaviors and decreasing the frequency of others through increasing the availability of dopamine in the synapses of brain circuits and results in a good feeling overall. In short, they get a momentary lift out of being indignant. For some pleasure-denying people, it's sort like an exercise-induced orgasm.
This is more or less what takes place when people use drugs to elevate moods. The drug hijacks and "rewires" the brain to increase the likelihood and frequency of emotional states and behaviors leading up to taking the drug. The result is an increased willingness to take the drug.
In general, any personality trait that becomes stable over time for an individual is a trait that is reinforced, for whatever reason, by the brain's reward systems. In a sense, some peoples' brains become hooked on being righteously indignant!
Righteous indignation certainly has the ability to provide a cheap thrill by being easily rewarding. For a short time, the righteously indignant person experiences a state of heightened emotional intensity which comes from a feeling of moral superiority over others. They get to be one up on an alleged perpetrator, possibly with a condescending lecture on the perpetrator's wicked ways. It provides them with an occasion to enjoy their fantasy of being much better and more moral than others. And that is a fantasy without any shame or embarrassment blow back, like having a secret fantasy of having a fantasy of hot monkey sex with three extraordinarily attractive guys.
My suggestion is that you look at righteous indignation in a practical way: All God's children need their reinforcements. It's not usually dangerous, it makes them feel good, it poses no threats to health, and it morally flails the unrighteous.
As for those that are their targets, they might also get their dopamine release from the delicious sense of feeling more wicked then they really are. Think of this, in some cases, as a win-win all around. We have a festival down in New Orleans where good Catholic girls can feel deliciously wicked by flashing their boobs on Mardi Gras day and the bluenoses can also feel so morally superior!