Now we all assume that this perfectly explains the people we disagree with. They are victims of conformity and group think. Thankfully we have reasoned opinions based in fact.
this "ten minute" philosophy video https://www.youtube.com/watch?v=js8E6C3ZnJ0 about "hegemony" makes a very similar point to Mark Twain, about how we fail to notice that the origins of our opinions and behavior are lost in the mists of mistiness.
The superficial aspects of how the point is expressed are very different and probably appeal to a disjoint audience. Every tribe has its own way realizing that the others are the victims of conformity and group think.
Cloistered by the filter bubbles. Though Twain's essay suggests it's not a new phenomenon. People tend to group together with those who believe similar things, each confirming preconceptions of the others. From inside of such a group it always looks like everyone else are sheeple that need to wake up.
Your are sheeple. But that doesn't mean that I am not. People are very painfully reminded of their imperfection on a daily basis. They don't always care to keep it in mind, or take it into account, but surely they are aware.
Are you saying that people are not aware that their opinions may not be as ironclad as they sometimes seem?