Bringing over my defense of Spuffy from the season 6 thread:

With regard to the Spike/Buffy relationship, I think a lot of people forget the context. He's not a human. He's a SOULLESS vampire. Which means that he can't tell right from wrong and lacks a basic part of his being that was torn out of him when he was turned into a vampire. This is bigger than any real world psychological problem, because in real life people can't have their "souls" removed. What we should be expecting from Spike is standard vampire behavior, trying to kill Buffy. Anything less than that, however horrible it would be coming from a human, counts as mild behavior by vampire standards. Spike, despite his lack of a soul, is unknowingly striving for redemption, reaching for greater levels of humanity than soulless vampires are normally capable of. Eventually he loses control because he's not clear where the line should be drawn and he attempts to rape Buffy and then, amazingly for a soulless vampire, he feels remorse and seeks to make amends by getting his soul back. What's happened here is that an inhuman monster has developed some humanity and tried to be a person, then failed at that and, feeling remorse, he's done what needed to be done to make him an actual person. Buffy's relationship with Spike redeemed a monster. The relationship cannot be understood outside the context of the show's vampire reality.

When people go on about how sick, perverse or abusive soulless Spike's behavior was, I feel like saying "What did you expect? He's a soulless vampire!" His behavior is actually pretty good a lot of the time compared to other soulless vampires on the show. Like, for example, soulless Angel. Of course once Spike has regained his soul, a change has been wrought in him greater than can happen to people in real life, because he's regained a core part of his self that had previously been supernaturally removed. He now has fully-functioning conscience and can tell right from wrong. Soulled Spike is no more responsible for soulless Spike's actions than a person who was previously insane is responsible for what they did while they were insane. Less responsible, actually, because insanity is a mere real world malady. Soullessness is a much bigger thing, with a whole part of the core self supernaturally ripped out. And this is why Buffy can forgive Spike in season 7. It's not at all the same situation as it would be if they were real people in the real world. The story is only made possible by the Buffyverse's supernatural reality. And it cannot be understood outside that context.

And what I said on the season 5 thread:

It's worth noting that's it's pointless to judge Spike as if he's a human being. He's a soulless vampire, therefore lacking a big part of his original human self. Behavior that would be horrible coming from a human being actually counts as good behavior coming from a soulless vampire. Normal behavior from a soulless vampire would simply be trying to kill Buffy, like other soulless vampires have done, such as soulless Angel. Spike's realization that he's in love with Buffy sets him on a long path to redemption, leading to his getting his soul back in season 6 and sacrificing himself in season 7. Love for Buffy has made a man out of a monster.