This comment has made me see Sirius' prank in a different light
I don’t think it grasped the seriousness and callousness of his actions when I first read the books. I used to think Snape was just an idiot for falling for it, and that Sirius just recklessly told him the truth, but now I'm not so sure.
From u/ItsASnitch:
/It is questionable if Snape did originally suspect Lupin was a werewolf.
The only implication that he knew we have is:
>“I know your theory,”
From Lily, which people take to mean he presented it to her multiple times for some reason. But this sentence makes perfect sense even if he just told it to her once prior to the conversation—which happens after the prank. So it's not a very convincing argument.
On the other hand,
Lupin calls it a "trick", Snape refers to it as "a highly amusing joke", and everyone else calls it a "prank" - all are implying there was some sort of deception going on not just "Hey there is a werewolf here's how you get to it." So yes, Sirius did deceive him in some way.
Luring someone or deceiving them to their death is still attempted murder.
Not to mention I don't think many people would consider even their bullies to go so far as to try to murder them. You are blaming Snape for assuming a classmate isn't going to use his best friend as a murder weapon. This is not an unreasonable assumption to have!
What Snape did suspect was that all of Marauders were doing something, he says they all sneak out at night and he saw Lupin with Madam Pomfrey.
>“They sneak out at night. There’s something weird about that Lupin. Where does he keep going?”
>"Sneaking around, trying to find out what we were up to… hoping he could get us expelled."
(The Marauders were animagi and were letting Lupin loose at this point. Snape didn't know that, just that they were all sneaking out to go after Lupin)
Lupin also implies Snape didn't know he was a werewolf before then.
>"He was forbidden by Dumbledore to tell anybody, but from that time on he knew what I was."
So Snape either:
-Didn't suspect Lupin was a werewolf (most likely)
-He did suspect Lupin was a werewolf but assumed he was also somehow restrained because the rest of Marauders were safe to go after him. So he most likely suspected what they were doing was releasing a werewolf. (Which was true)
Whichever it is - it is Sirius who is at fault and deserving punishment for tricking another student into a deadly situation and nearly turning his best friend into a murderer./
This comment convinced me Snape wasn't at fault for falling for the trick, but I was still conflicted about Sirius' motivations. If it was a reckless heat of the moment decision, he would've regretted it right? But JAMES was the one who recognized the gravity of Sirius' actions and saved Snape, not the other way around. Sirius also never regretted it and maintenance even as an adult that Snape deserved it just because he was trying to get them expelled (after years of bullying). And the worst part is, they probably did deserve expulsion because Lupin had "many near misses" aside from Snape where he could've bitten or killed someone.
It also didn't make sense to me why Sirius would tell Snape the secret if he was just trying to give him a scare. In that scenario, Snape would've gotten confirmation of Remus' secret and told the whole school. But if he ate him or bit him......the problem of Snape stalking them would've been solved. I think Sirius thought this attempted murder was him doing Lupin and the rest of the Marauders a favor.
There's no scenario in which you can really give Sirius the benefit of the doubt here.