Mainstream media often find it easy (and profitable) to broadcast something mildly offensive to a wide audience, so making a certain group of people feel they "deserve" to be outraged. Then they broadcast that outrage back across the population in a way that outrages yet another group of people -- who otherwise may not have been outraged at all and blame the first "imaginary" group. This then evokes a widespread sense of frustration, injustice and victimization.
Social media is as much to blame as mainstream media. People may get addicted to this type of "outrage," because it tends to generate an emotional high and sense of self-righteousness and moral superiority. As political cartoonist Tim Kreider wrote in the New York Times: "Outrage is like a lot of other things that feel good, but over time devour us from the inside out. And it's even more insidious than most vices, because we don't even consciously acknowledge that it's a pleasure".