Well, real life tells us different. Real life tells us that heroes come in all shapes and sizes and personalities and are not cookie-cut out of some romance novel image.
So, for those dunderheads who haven't "gotten it" yet, here is The Princess's version of "Severus Snape 101 - or How to Know a Real Hero When You See One."
*Snape was not suppose to be warm and fuzzy and likeable, so it doesn't matter whether you personally like the character or not. He is what he is, but that does not take away from his courage, determination, loyalty or devotion to what he had to do. That does not take away from what he accomplished. And, it certainly does not take away from the fact that he put his life on the line every moment that he spent as a double-agent.
*Snape was not suppose to be perfect -- that was part of his appeal, that he made mistakes, like the rest of us human beings, but went on to try to make amends.
Don't look for a saint here, because you're not going to find one. You're going to find a flawed human being who screwed up royally during his youth (now, how many famous and heroic people can one find throughout history who screwed up royally during their teens or early 20's??? I'm sure there are quite a few more who did than those who didn't.)
But, he saw the error of his youth, in somewhat the same way that Dumbledore saw his...through the endangerment/loss of someone he deeply loved. That puts him in some pretty good company right there, it seems to me.
*Snape's main focus was not to be a good teacher, although, from what we see, he was respected by his colleagues and must have done a fairly decent job since most of his students went on to pass their OWLS and NEWTS in Potions.
He was no more a bully than McGonagall, he just lacked her finesse. And, he was no less fair, that we can see in canon. He gave detentions to his own House (starting in SS/PS, as Draco could not have served the detention given by McGonagall for breaking curfew without his Head of House agreeing to it. We see support for this statement in CoS when Snape wants to expel Harry and Ron for flaunting several wizarding rules and arriving in a flying car. Dumbledore informs him that their punishment is up to the Head of their House, Professor McGonagall and not Snape's decision to make).
*Snape did not set out on his mission for Dumbledore to "redeem" himself, but to atone for being what he'd allowed himself to become, and for having even a part in Lily;s death -- the "redemption" happened because he was truly sorry for his past.
Severus Snape never forgave himself for carrying the Prophecy to Voldemort and setting that whole series of events in motion. Even though he did everything he could to protect Lily -- and her family; even though it was one of James Potter's good buddies and fellow Marauders, Peter Pettigrew, who finally brought about their deaths by breaking his vow as Secret Keeper and disclosing their location to Voldemort, Severus Snape always seemed to keep a sense of guilt for even having been a part of Lily's dying.
But we know he also changed his view on the value of all human life, not just Lily's, when he is "horrified" as Dumbledore explains that Harry must die. When Dumbledore tells him not to be shocked and then asks him how many men and women he had watched die, Snape replies, "Lately, only those whom I could not save."
*Snape was not supposed to go "have a life" between Voldy Wars. I would love to see an interview with a true "mole,' a spy so deeply entrenched that neither side, other than the few who really know their mission, (like Dumbledore) trusts them completely. Then we might get a sense of what Severus Snape's life was like during the lull between Voldemort's temporary vaporization and his return to full power.
Dumbledore knew the Prophecy and he knew Voldemort would return. If he knew, Snape knew. While we aren't told exactly what he did for those years before Harry arrived at Hogwarts, I would think he spent them working with Dumbledore to hone the skills he would need to resume his role as double agent.
In particularly I would think he'd be working on his Occlumency skills, his dueling skills, and his contacts with the likes of Lucius Malfoy and other former Death Eaters. He had to maintain the "loyal but not quite sure when Voldy was coming back" attitude that people like Lucius had so as not to arouse suspicions, and so he would be able to go to Voldemort, as he did in the graveyard the night of the Dark Lord's rejuvenation, and have a feasible cover story to tell.
*Snape was suppose to protect Harry, not be his pal. Harry's protection was his primary objective -- this is what he'd promised to do, and that is what he did. And, he carried out his promise up to the moment of his death. Then, so that Harry could complete the plan that Dumbledore had set out, Snape gave him the information he needed, as he was dying, in the form of his memories.
*Snape gave Harry a gift through his memories. But, he also gave Harry more. He gave him a view of his mother, as a young girl and teenager, that Harry would have never seen otherwise. He also showed him the reasons that he had done many of the things that Harry detested him so much for.
When he said "Look...at...me..." and gave Harry 20 specific memories, only a few of which pertained to information Harry needed, I feel he was asking Harry to look at him, Severus Snape; who he was, what he'd done, and how he'd tried to make up for it. I think he was asking for Harry's understanding, and maybe even his forgiveness.
I know there are those who don't think that Snape ever cared for Harry. I don't think he did at first, not until he gave him the Occlumency lessons and saw how similar their backgrounds were and that Harry had not come from some plush, pampered existance like James, and with an ego big enough to fill the Black Lake. Snape saw the "real" Harry then, and, if Harry hadn't infuriated him by invading his privacy and looking into the Pensieve, I think there might have been a less confrontational attitude. But, once that was done Snape had no choice but to keep Harry at arm's length because of the mental connection to Voldemort and the possibility of Voldy perceiving too much through Harry's thoughts.
But, when Harry nearly killed Draco using Sectum Sempra, a spell from Snape's old Potions book, he didn't take him to Dumbledore, he didn't try to have him expelled for nearly killing another student, he gave him detention, in his company, every Saturday until end of term. While this may sound like a terrible thing, I think to Snape it meant as long as Harry was with him he wasn't in danger. And, that made his job just a bit easier. There were many things he could have done that were much worse.
Many point to the times that Snape tries to spoil Harry's fun by trying to get him off the Quidditch team. Quidditch is a dangerous game, at best. And, if you happen to have a Dark Wizard and/or his henchman after you, that can make it even more so. We see this with Quirrell and with Dobby (even though Dobby was trying to help, he still did several things that put Harry in danger).
Yes, Snape tried to get Harry expelled, how awful. But, both McGonagall and Dumbledore also tell Harry, at certain times, that his continued behavior might lead to him being expelled. Also, as Snape was a "friend" of the Malfoys, if Dobby knew in CoS that something dangerous was going to happen, Snape probably knew it too. Maybe not to the same extent, as I'm sure the Malfoy's ignored Dobby's presence and spoke freely in front of him. But, I can imagine that Lucius, ever the braggart, didn't let something slip when talking to Snape.
But, Snape also knew that Harry was safe at his aunt's home, which had a protection provided through his mother's sacrifice of her life. To Snape, it might have seemed the safest place at the time, since Harry seemed bent on breaking rules and pursuing adventures, might have been there.
*Snape saw James in Harry and reacted to that. He probably couldn't help it. The physical appearance, except fot "Lily's eyes," seemed to be most striking. Everyone noticed it and mentioned it.
With an uncomfortable history of being bullied..."tormented," to use Harry's own word...by James and the Marauders, seeing 11-year-old "James" sitting in front of him again had to cause all kinds of flashbacks and emotional turmoil for Snape. That he couldn't let go of his school time traumas might be considered a flaw. But, even Albus Dumbledore says that some scars run too deep to heal.
And, there was also Harry's penchant, like his father, for disregarding rules and thinking they only applied to others who were not on whatever "mission" he was on at the time. So, small wonder that Snape saw so much of James in Harry.
So there you have it, dunderheads. "Snape 101."
And, if you still can't wrap your small, closed little minds around it, just remember this: in the end, Harry Potter named his second son after two Hogwarts' headmasters, one of them a Slytherin, and, probably the bravest man he ever knew. So that kind of says it all, doesn't it?