In my country, the US, many people once believed that slavery was morally wrong, but still argued against freeing the slaves because they might try to take revenge on the rest of the population. Those fears were, in fact, confirmed on several occasions. And even today, areas with a high population of descendants of slaves fare far worse by almost every economic and social measure.

Freeing the slaves (a task which required us to fight the deadliest war in our history) was still the right and necessary thing to do. "You broke it, you bought it."