I have never encountered a fandom, especially on Tumblr in the age of social justice awareness, so intent on denying a victim of sexual assault is in fact a victim of sexual assault (JKR using the fade to black in a children’s book and Snape’s trauma response to Harry using Levicorpus is more than enough evidence to infer that James did in fact go through with his threat to remove his underwear). I can’t fathom it. I distinctly remember when OOTP came out and readers were horrified because the implication of that chapter could not be misunderstood. What on earth has happened in the years since?!
Ah but you see, social justice awareness but only for those that are deemed to be deserving of it.
Tumblr is also right in the age of "everyone who isn't perfectly perfect deserves to die", so that's why we also see plenty of Marauders stans say that Snape deserved everything that happened to him.
The logic is that since Snape was a bully and an asshole in general as an adult, his 15 year old self deserved to be bullied, almost killed and assaulted.
Also, it ties right in to the idea that James Potter and his gang of merry dumb fucks are the social justice warriors. Since they're on the "right side", fighting against muggleborn prejudice, against Death Eaters, against the Dark Arts in general., then everyone who opposes them is not only wrong, but the most evil people to have ever existed.
Of course, we know that the Marauders didn't attack Snape out of some fucked up sense of justice (not that it'd be better if they did anyway), even James himself doesn't even try to defend what he's doing, but Marauders fans love their characters so much that they will also ignore what those characters themselves say.