It's not weird at all, it's basically normal human group psychology, as near as I can tell, looking through history. Your in group has a set of beliefs, the out

It's not weird at all, it's basically normal human group psychology, as near as I can tell, looking through history. Your in group has a set of beliefs, the out group has other beliefs, it's what makes them others and worth competing against/destroying if needed. The major societal improvement that is science gives one a decent algorithm for changing ones mind. I believe being able to point at the algorithm is a very overlooked part of why we began to be able to change our minds more effectively and less violently as a society.