It’s one of the things that drives Angel crazy; the way Spike flirts with everyone, indiscriminately, promiscuously. There are promises in the way tongue touches lip and words ooze like caramel from behind; promises that aren’t really being made, let alone kept.
There was a time when the fighting was what got him hard, but not now – damned soul and all its softness. Now he’s perpetually aroused by the way Spike winks at Fred or smiles at Gunn, the way he touches Wesley’s shoulder. Spike’s a whore and always has been. But he’s not Angel’s whore, not anymore.