>Isn't that what negotiation is about, when dealing with someone who won't effectively communicate their thoughts?

No, negotiation is the process that happens when you and the other party have decided you want to work out a mutually acceptable agreement. The other person in this situation has not decided to do that, and so the trick is how to get the him to that point. I think Zelphyr's approach would be a lot more likely than yours to have that effect.