I could easily believe that Snape has autism. I am not quick to diagnose characters, but I’m also not going to suggest characters can’t fit a diagnostic criteria of any mental condition that isn’t explicitly stated. It can put a character’s behaviour into perspective.
I really think he really struggles socially. I think he genuinely doesn’t get what the problem with practicing and liking dark magic. I could see him doing something messed up to a frog like slowly turning it inside out or making it burn alive very slowly (observe how it doesn’t notice it’s in pain, because it gets accustomed to it. That’s what really fascinates him) and it really freaks Lily out! She is very cross and tells him to stop it right now or she won’t talk to him for the rest of the day. I think Snape wouldn’t get it. He does not understand why Lily is so angry at him for doing this to the frog.
He’d be like, oh so I can’t do a magic trick on a small animal but it’s okay for James Potter to put a jinx on him that makes every footstep sound like flatulence and make everyone laugh at him? Lily says that they’re completely different, one is a stupid joke that’s meant to be funny and the other is torturing the frog. Snape says how is that funny? And this is meant to be funny too and it’s more interesting than imitating bodily functions. I think Snape genuinely wouldn’t get it. How is what James did is funny and makes people like him more, but what Snape does makes everyone think he’s creepy and avoid him?