Suffice to say there are people out there who refuse to admit Snape has ever done anything wrong and try to make excuses for his bad behavior, even if it means victim-blaming the shit out of the other characters.

Those exist in every fandom, alas (I'm thinking of the crowd that advocates "the Phantom was a poor persecuted innocent, and we will prove this by explaining how everyone he threatened or murdered was evil and perverted"). When people become passionate advocates for a given character, they have a tendency to try to put them on the right side of every argument... even if this results in a version of the character that's totally unrecognisable from the canon that supposedly made them fans in the first place.

Snape is not a nice man -- it's more or less his defining characteristic. His reflex reaction to just about anything is unpleasant.

On the other hand, like anyone else, he doesn't see *himself* as the villain and probably finds his own actions entirely justified, so the challenge in fan-fiction is to show the gap between self-perception and reality without simply cheating and writing a saintly misunderstood Snape...