I'm reading a book titled ORIGINALS: How Non-Conformists Move the World (by Adam Grant). In it, I've come across this passage that seems to illuminate something visible in our politics these days.
In a chapter that starts out with a discussion of how the 19th century movement for women's suffrage set itself back with the hostilities and divisions that arose among its leaders, between more radical and more moderate elements, Grant goes on to say:
We assume that common goals bind groups together, but the reality is that they often drive groups apart. According to Dartmouth psychologist Judith White, a lens for understanding these fractures is the concept of horizontal hostility. Even though they share a fundamental objective, radical groups often disparage more mainstream groups as impostors and sellouts...
White noticed horizontal hostility everywhere. When a deaf woman won the Miss America crown, instead of cheering her on as a trailblazer, deaf activists protested. Since she spoke orally rather than using sign language, she wasn't 'deaf enough.' When a light-skinned black woman was appointed as a law professor at one university, its Black Student Association objected on the grounds that she wasn't black enough. A radical environmental activist dismissed the more mainstream Greenpeace as a 'mindless monster motivated by eco-buck profits' and 'a dynamic threat to the integrity of the green movement.'...
[Research conducted by White revealed that} Vegans showed nearly three times as much prejudice toward vegetarians as vegetarians did toward vegans. In the eyes of the more extreme vegans, the mainstream vegetarians were wannabes: if they really cared about the cause, they wouldn't eat animal products like eggs. In another study in Greece, members of the most conservative party judged the most similar party more unfavorably than they did a progressive party, and members of the most liberal party were much harsher toward the progressive party than toward even the most conservative party. Orthodox Jews evaluated conservative Jewish women more negatively than Jewish women who didn't practice or observe religious holidays at all. The message was clear: if you were a true believer, you'd be all in.