Okay a few things people are forgetting:
1. Snape was a child of an alcoholic and abusive father who was a Muggle, who both abused his wife and child as hinted in the text. Shapes only connected with the muggle world was basically a father who hurt him and his mother. The mother also seemed to be not to nice to the son, and, as based on his clothing, did not care to clean or help him be a better person. On top of that Lilly's sister was treating her horribly when he found them and pretty much his view of muggles was shaped for the most part.
Petunia wasn't treating Lily horribly. Petunia was afraid of and fascinated by Lily's abilities. She was also concerned that Lily was rulebreaking, because their parents had told Lily not to use her powers in public. Petunia clearly became envious and didn't want to be separated from her sister, so she wrote a letter to Hogwarts asking if she can go with Lily and learn to be a Wizard too.
Snape was stalking Lily, watching her from the bushes, and he opened their mail and read Petunia's gently-worded response letter from Hogwarts, and showed it to Lily for the sole purposes of laughing at Petunia, whom Snape considered a Mudblood. Imagine, a Muggle having the audacity to wish they were a Wizard. When an upset Petunia tried to insult Snape's clothes, 10-year-old Snape in a rage hit her in the head with a tree branch and made her cry.
Snape may have had terrible parents who sent him down the wrong path in life, but he was clearly on the incel/Nazi path long before he ever met James Potter.
2. Lilly was the only friend and outside connection to the world that Severus had. It's shown in the books that, like Harry, he's treated like shit for being poor and who he is. When he and Lilly were on the train James and Sirius came to the back of the cars they found them and started to mock the hell out of Severus and Lilly (for being around him).
Lily was crying on the train to Hogwarts, because Snape had made Petunia hate Lily (in Lily's own words), and Snape told Lily that she
must join Slytherin house (because that will solve the problem of giving a damn what your Muggle sister thinks).
James and Sirius were already in the same car, sitting across from the two of them, when James expressed disgust at Slytherin, and Sirius said that his parents were gonna try and railroad him into Slytherin, and James (having been asked by Sirius) said he was aiming for Gryffindor. Snape insulted James, and James insulted Snape. Then Lily decided to break things up by moving herself and Snape to another car.
Lily joined Gryffindor, and (knowing full well that she went to Gryffindor) Snape joined Slytherin, because his hormones hadn't fully kicked in yet, and his Nazi side was bigger than his incel side.
5. Snape fell in with that group because that was how he thought he could keep from being targeted by the pure bloods himself.
That's BS. There's no indication that Snape was bullied by the Nazis into becoming a Nazi. The closest we have to that is that Snape recognized that being a half blood put him on a lower tier than the pure bloods, so he started using the name "Severus Prince" instead of "Severus Snape", to show that he had no allegiance to his filthy Muggle father. He was one of the "good" half bloods.
Snape was a Nazi at age 10. He knew for certain that he wanted to be in House Nazi, that he hated the members of Gryffindor, and his only regret was that he wasn't able to drag his waifu into House Nazi with him.
Pre-war, he willingly joined the Hitler Youth while he was still in school, and quickly advanced to become the right hand man of Wizard Hitler, a man he greatly admired.
Even before the "bullying" incident, Lily pulled Snape aside and asked "What the fuck dude? What are you doing with those Hitler Youth guys? Have you
seen what they are doing to people? They are literally evil." And Snape says "It's just pranks bro."
The most damning thing about the James Potter "bullying" incident is that James used the spell that Snape invented. James had to have seen it in use often enough to learn it. Yes, he enjoyed using it on Snape, he enjoyed the feeling of being the bully and the bad guy, but that does not make James and Snape anywhere near the same thing when James was just giving Snape a taste of his own medicine.
And, James was eventually sorry that he did that to Snape.
Snape meanwhile built and carried around at school a laceration shotgun, capable of inflicting wounds that can never be healed, and/or maybe death.
"What's your problem with Snape?" Lily asks of James. "I dunno, maybe the fact that he exists" answers James. That
sounds like bullying logic, until you discover who Snape actually is and was as a person.
Snape went on to join the Death Eaters, became Wizard Hitler's right hand man and was directly involved in uncounted acts of murder and torture.
He gave Voldemort info that he knew would lead to the murder of children and families, and only became concerned when he learned that his unrequited waifu love was among one of the family members. Snape's attitude was "Fuck Neville Longbottom. Fuck Neville's parents. Fuck baby Harry. Double-fuck James Potter. They can all die, all of them. But please someone, save Lily Evans-Potter!"
Snape swore an oath to Dumbledore, and he openly assessed the value of his incel obsession at "infinity", so Dumbledore claimed ownership of his soul in exchange, and Snape was like "Damn your math, but you can't argue with math, so okay." Snape stopped being a Nazi because his incel side had grown more powerful than his Nazi side, and Dumbledore took advantage of that.
There's no evidence that Snape ever did any personal growth. He tormented Neville (a kid whose parents were tortured into insanity by Snape's friends thanks to Snape's direct actions). And Snape's last act was to stare in Harry's eyes as he masturbates to the fantasy image of Harry's dead mom, because "Fuck all of you, I have earned this." Also, Harry names his kid after Snape, because WTF Harry?
Snape was trash from A-to-Z, and that includes his school years. James Potter at his worst could not even hope to be as bad of a person as Snape was.
