Yes, but the world isn’t split up into good people and Death Eaters,” said Sirius with a wry smile.
This is, in my opinion, the single most character building line of dialouge that comes from Sirius Black (who, of course, I love). Why? Because it gives us an insight into his family life and upbringing that no other scenes do. Let me explain.
As we get to know Sirius, we learn that he passionately hates his family, and they – for the most part – return the favor. He mentions leaving home to live with the Potters at 16, he’s been blasted off the Black Family Tree, and it’s a toss up who’s madder that he’s back in Grimmauld Place – Sirius or the portrait of his mother. Most people have interperted that to mean that Sirius, from the time he was young has been different from his family and abused for it – a little bit like Harry, honestly. Treated terribly thanks to not fitting into the family mold, if you will.
But what if that wasn’t the case? What if he entered Hogwarts his first year as secure in his family’s beliefs as, say, Draco Malfoy. And he happened to meet James Potter on the train and hit it off with him – maybe before either one of them knew who the other was, because let’s be real there’s less than 2 dozen wizarding families they would have recognized each others’ names – and then he got sorted into Gryffindor, where blood purity matters much less than what you do with all that pure blood. And he met Remus Lupin, who was a half blood (and a werewolf, but I doubt anyone figured that out right off), and Lily Potter, who was a Muggle-born, and realized that maybe his family WASN’T totally right and maybe blood status wasn’t the end-all-be-all of wizardry.
And he probably didn’t start standing up to his parents right away. But you know he would have because COME ON Sirius is a total drama queen (not unlike his godson, to tell the truth). And Sirius would have been like the stereotypical teenage girl who just discovered feminism and is yelling at her dad about the patriarchy over dinner. Until finally sometime around his 5th or 6th year he just LOSES HIS SHIT and tells them that he wasn’t going to sit around pretending to agree with them and they had to choose between their blood purity beliefs and their son. And they chose their beliefs.
And Sirius knows his parents don’t think of themselves as bad people, and he has a hard time seeing them that way either because they’re his PARENTS and he LOVED THEM until this became a wedge between them. Even if he doesn’t agree with their views, he knows the good in them, and the love they showed him. And he could have been that person – he was on track to becoming that person – except for a chance meeting and a lucky Sorting. That’s why it’s so important to him that Harry knows there’s a distinction between bad person and Death Eater (although significant overlap). That’s why he is so miserable at Grimmauld Place – because he has terrible memories of his parents, sure, but he also has good memories and that’s what hurts.