The show Buffy is remarkably rich in interpretive material. I would never deny the many ways that Spike specifically (as the topic of this thread) conforms to and also confirms many a theoretical interpretation in surprising ways. This thread seemed to digress, so I apologize for not addressing specifically the OP, but I just wanted to say that, while I find academic/theoretical readings worthwhile and gainful with regard to this show in particular, I do also feel like it is equally fair to interpret and also judge the merit of a show (or also just specific features of a show) on purely aesthetic grounds too. The one doesn't refute the other.
Why do I say this? I say this because, over the course of reading many, many debates concerning Spike specifically, I get the strong impression that perhaps the difference in perspective in the way the fan base divides on topics like Spike boils down to this difference, or differences in a very similar vein. So for example, in my case, I've learned a great deal from Spike over the last year by using a Foucauldian approach to better appreciate the role that power relationships have in constructing various modalities of subjectivity, and how this effects the kinds of things you can know, the threshold of what counts as 'ignorance', and so forth. The material for such an inquiry is there in the text, without a doubt. As I said, Buffy is rich for interpretation. But on the other hand, I have to admit to feeling conflicted sometimes because on an aesthetic level I tend to judge Spike and Spuffy often as an aesthetic failure for me, despite my intellectual curiosity in Spike and Spuffy and all related matters. So I'm divided.
To use an analogy, it's like the experience of going to an expensive Michelin star restaurant and not enjoying yourself. The food may have been prepared with all the newest cutting edge molecular gastronomy techniques, and the skill in the technique was everywhere evident, but despite all of that, in the end, you didn't enjoy the flavors put forward in the meal. It didn't taste good. Or to put it a little differently, it was a technical/theoretical success, yet despite that, also nevertheless an aesthetic failure also. Many Spike centered debates seem to me to pivot on something similar to this: we want different things from the same show, and the arguments we have to support our pleasure or displeasure follow from the way we prioritized what we wanted from the show to begin with. Then what comes afterward is our justification for these biases. Anyway, this is just my impression of this thread and many other similar ones. For whatever it's worth.