"Get off your high horse" is an idiom
people retort with in an argument when the other person is acting like a holier-than-thou being when in
reality, they aren't. To put it in a simpler manner, to tell
people to stop acting as if they're the top authority when they aren't.
Person A: "I am completely
entitled to go around dismissing
people when they do something completely
normal just because they're wrong and I'm ultimately right."
Person B: "Get off your high horse."