You read me enough to know what I'm going to say. In a dominance hierarchy, those on the "higher rungs" have the "right" to abuse those lower down, who are expected to take it stoicly. But when people don't take it in silence, it upends their expectations of how the system works.

They subconsciously believe that the world is both by and for them, because that still gets regularly reinforced in all sorts of ways. It makes them upset to have that notion challenged.