During all of time there has always been a good cause and a evil opposition to this as when the blacks wanted equality and the government did everything they could to stop this from occuring.
However typically there is always someone during these times to fight the injustices of the as Martin Luthor King Jr. who with the support of his friends and family was able to peacefully get African Americans the rights they types of people are called heroes simply because they fought for what they believed some would argue that the people we call villains that fought against what is believed now should also be called heroes because even though they fought for a unjust cause they gave us the motivation to fight against this.
In the Wizarding World there has always been two causes,the fight for muggles and muggleborns and for light has always been champions for these beliefs such as Merlin and the greatest hero to fight for this cause was the one that wasn't a hero,Harry James was one of the few that understood that sometimes to make a better future you can't be a hero but that you have to sometimes be worse than the person you're fighting to truly win.
Maybe that's why when we speak of Lord Harry Potter-Black Peverell we spoke of him as if he was worse than Lord in reality he did what was needed to make the world a better place,a place where a muggleborn was equal to a pureblood
Many do not consider him to be the reason of this however he is the reason for it because he could have chosen to be average but he knew for most to have a normal life he could when he learned something from Dumbledore he knew what choice he had to make.