There was once a country in which the priests decreed that any male child born on the third day of the month was entitled to wear green shoes. There was no additional money, better food, housing or education, but only those people so defined were entitled to wear green shoes. A thousand years passed and the religion died and the only hint that it it had ever existed was the green shoes rule. One year there was an election and the winning candidate promised to repeal the green shoes rule.
Those entitled to wear green shoes were very angry and they formed a secret society to protect their ancient rights. One member of this society assassinated the new president for daring to suggest that the world could be changed.
Moral of the story: Anyone who sees their position and privilege threatened is willing to kill in order to protect the difference, no matter how notional.
Every change for the better has been opposed by those who think their position is in some way threatened