I think it's worth a try. Also, there are people here who would be devastated if we didn't at least try what we could before resorting to killing him, and I need to be able to look them in the face and tell them I did everything I could.
[God knows Penelope's going to be devasted enough at what he's doing to Spike without telling her; he can't imagine having to tell her he just staked the guy without even trying anything else.]