He just didn’t have all the information.
Harry’s negative attitude and feelings towards Snape were completely justified based on how Snape treated him and his friends. And don’t give me any of this “Snape was only shitty to Harry because Harry had a bad attitude” garbage. No, Snape was not “putting up with Harry’s bullshit”. I’m going to lose my mind. You’re talking about an adult interacting with a child.
The very first time Harry saw Snape, Snape looked at him with enough venom that Harry knew he didn’t like him. By the end of their first lesson, he knew Snape hated him. This adult he’d never met before. How freaky would that be?
Snape’s first words to Harry were public insults. Harry was eleven. He was a small child. Harry did nothing, absolutely nothing, to provoke Snape. Snape saw his name on a list and said the “Our new celebrity” line, humiliating him in front of Draco and his Slytherin friends. Then he asks Harry a question he knows he’s going to get wrong and mocks him when he does. And when Neville messes up his potions, Snape snaps at Harry for not stopping him and accuses him of letting Neville make a mistake so Harry would look good in comparison. And he takes a point. That’s just their first interaction.
That kind of thing continues throughout. And yeah, eventually Harry started answering back. Good for him. Standing up for yourself against a bully is brave. It’s not “bullshit” Snape had to put up with.
I swear to god, if I see another person claim that readers only have a negative view of Snape because the books are from Harry’s pov…
Love Snape. It’s fine and good to love him. He’s a fascinating character, he’s got wonderful good qualities as well as deeply negative qualities. He’s got qualities that make him sympathetic despite his nastines. But don’t erase his nastiness by claiming Harry’s pov wasn’t reliable. (Harry is NOT an unreliable narrator. He doesn’t lie to readers or intentionally withhold information from them. His narration is reliable based on what he experiences. If he’s wrong, it’s because he doesn’t have all the facts. Like any narrator.)
This makes me every bit as cross as “Snape was an incel who just wanted to fuck Lily”. It’s no better than that. When you say stuff like that you’re providing fodder for the people who think Snape fans are abuse apologists.