Perceived injustice is the root of much conflict. Our world too often remains a dog-eat-dog battleground, a Social Darwinist killing field where the weak and unfortunate become nutrients for the advantaged.
Those born in the USA have opportunities unachievable to most people born in Somalia, for example. We've created a global system that perpetuates unjust favoritism. Some people claim a mandate to steal land or property (Fascism, "manifest destiny") or to otherwise oppress (perhaps because their relatives suffered, or a benefit of God's Will). Further subgroups manipulate the rules: banking executives rely on market discipline when pricing or refusing loans, but when their own jobs become exposed, finagling subsidies & new rules with undiminished self-aggrandizement.
Always around the corner lurks another band of thieves, eager for wealth. People will struggle with injustice. Those with looted treasures can never be quite secure. We can only try to make better systems; havens of justice.