It's sort of logical: if a "bad thing" is observed, a "good" observer must feel bad as a negative reinforcement against the "bad thing". Ideally the pressure of the negative emotions must force the "good" observer to stop just watching and go fix things, and afterwards prevent the "bad thing" from occurring again.
This works in simple cases, like spilling your drink: it: it feels bad, the feeling makes you clean it up, and be more careful.
It fails in cases where the immediate effectual action is impossible, or not known. The only reasonable course of action then is to spread the word, because you can't actually fix anything.
And here ingroup / outgroup signaling jumps in! Feeling bad about some issues becomes a signal of group belonging, a kind of virtue signaling. Not feeling bad and not expressing outrage becomes suspicious, if not defiant. This is one of the streams that feeds the outrage machine.
This works in simple cases, like spilling your drink: it: it feels bad, the feeling makes you clean it up, and be more careful.
It fails in cases where the immediate effectual action is impossible, or not known. The only reasonable course of action then is to spread the word, because you can't actually fix anything.
And here ingroup / outgroup signaling jumps in! Feeling bad about some issues becomes a signal of group belonging, a kind of virtue signaling. Not feeling bad and not expressing outrage becomes suspicious, if not defiant. This is one of the streams that feeds the outrage machine.