I don't really care to be honest. But the motives of a souless vampire come across different. Vampires are evil, so even vampires who are in love say evil things like calling her a bitch and "saying he'll teach her a lesson." I think the real revelation in this is how self centered most souless vampires are, either way he was planning on teaching her lesson or proving a point. As a vampire, he wasn't getting a soul to prove that he loves her, he got a soul to shove everything back in her face, to show that he is just as good as her. So either way you like at it, soulless Spike didn't have a good meaning selfless intent, he meant on getting revenge. So it had nothing to do with love, but more infatuation. Of course that all changed one he got his soul