I just stumbled on a useful idea of Freud’s called “the narcissism of minor differences”. File under “I never knew there was a word for that”. It seems like such a prevalent part of human experience & behavior that it seems obvious that there should be. Here’s a succinct definition which I lifted from here:
Why are Republicans so hateful toward Bill Clinton when he is more like them than virtually any other Democrat? He has pushed through many of their favorite policies, such as cutting welfare, promoting the North American Free Trade Agreement and proposing that portions of Social Security reserves be privatized. You would think Republicans would regard him among their favorite Democratic presidents. Instead, the opposite is true. They seem determined to kill him politically through character assassination fueled by a hatred that is hard to understand.
Sigmund Freud had a brilliant explanation for this type of animosity: the narcissism of minor differences. The psychoanalyst contended that human beings express their most virulent hatred toward those who are just slightly different from themselves. This is because slight differences pose a greater psychological threat to ones core sense of self (ergo: narcissism) than those who are extremely different from ourselves. Freud used this concept as an explanation for the most heinous forms of aggression.
I originally saw it in this Globe article about transatlantic relations.