I'm about to rant, you have been warned.
This is an entire group on LJ:
Welcome to [info]deeply_horrible, a community devoted to characterisations of Severus Snape as a bastard. While we acknowledge and honour Snape's bravery and self-sacrifice, we also accept that he's not a particularly nice or pleasant person. To put it mildly. In short, we're intrigued—fascinated—by the fact that Snape is profoundly flawed and find his flaws worth exploring in a way that doesn't minimize them, because they are so much a part of him (and, it must be said, we enjoy playing with the less than savoury aspects of his personality). If you feel the same way, we invite you to take the Bring Back the Bastard Challenge by creating works of art, fic, and meta that celebrate Snape's "deeply horrible" character.
Uh, where? Because the Snape I read (and like) is fundamentally a good person. He's not sadistic, or a horrible person. He never stalks Lily. He doesn't want James or Harry to get killed, unlike what Dumbledore says.
Contrary to what fandom likes to think, the only person he has ever killed was Dumbledore. He was not on the front lines (also, I don't think the Death Eaters were Evil). He frequently goes out of his way to save the lives of people he hates, putting his own into jeopardy in the process. He does everything he can to save people from pain - he genuinely doesn't want to hurt people. He's nice and caring to the people he likes. He's no worse a teacher than McGonagall or Flitwick.
There is a fundamental difference between him and Dumbledore: Dumbledore will do whatever has to be done for the Greater Good at the expense of others. Severus does whatever has to be done at the expense of himself.
He's not a liar or manipulative, he's honest and painfully direct (in his childhood/teens and when his spying allows him to be). He's has a huge capacity to love, and is extremly loyal to those he does love. It's as RiddleTM said in one of their Severus songs: "You are sweet and you are kind".
Yes, he's snarky. He has a very dry sense of humor, and is extremly sarcastic. He's intellectually brilliant, and socially awkward. He's a loner. Whitehound characterized Severus to duj as "Doing the Right Thing with exemplary courage whilst bitching about it the whole way" - to which she replied "That's our Snape, all right".
So we have a sarcastic snarker with a big heart. What's the problem?