Maybe they were wrong or harmed by certain parts of the heritage and that can act as reminder or become a provocation.
This is why in everything we do, we do it fairly and not wrong anyone. The victim of the wrong deed could bear longlasting grudges, and the wrong deed can be used against the wrong doer in the future... Even the enemy can take advantage of this and constantly remind the victim to keep the parties involved divided. Or there could be false representation of true history to achieve thesame goal.
But if evil doer was justly punished in the past and the intention of the punisher was good, the proof will be in the good outcome, and it will be hard to erased or hide. This can be used as evidence why justice was done in the past. But everything should be done morally or with good intentions rather than in hurtful prideful or provocative ways. Otherwise that become loopholes for the enemy to take advantage of to keep both divided and weak.