Michael, what you are asking is rather a personal question, legalities aside these are decisions which are done in a case by case basis and have more to do with emotional concepts than with the issue at hand.

Obviously you feel strongly you would not give the negatives, me I rather choose the battles I want to fight, in some cases I might surrender the negative, in some I might not. Regardless of my reputation I would weight what is the greater benefit for me in the long run, if this place I shot belongs to someone who is well known in the local community and returning the print and an unusable negative will generate good will towards me and allow me to continue visiting the place in peace I would definitely do so, if I am in Timbuktu, take a pic and a year later I get a letter demanding the neg and the print, most likely my response would be different. It is all relative.

In Robert's case, since this is a person in his same community, which for purely selfish reasons can damage his emerging reputation, I would certainly try to meet them half way. I think he needs to look a few years down the road and how the opinion of this one woman can affect him. Unfortunately this kind of things have a way to come back and bite you in the ass. I can just see him asking another woman down the road to pose for him and her saying, "aren't you the guy who photographed xxxx and then refused to help her and ruined her relationship?"

However right we think Robert is, I am sure this is not the same story that these other two people are saying. IMO, taking a hard line in this situation has the potential to damage him more than the benefit he might obtain from keeping the negatives.