So, like an idiot I sold an item on ebay rather than the forums.

I posted multiple pictures, mentioned and pictured damage to the finish, and sold it as "for parts".

So this idiot (with, may I say, the WORST username ever) sends me a handful of messages offering to buy it outside Ebay for under my starting-bid price. Then he bids on it and wins. I mailed it out, and it arrived within 3 days. At this point, he leaves me neutral feedback based on the issue that was pictured/described, and sends me an email stating that he will change it to a positive if I give a full refund, and a negative if I don't. Then (after feedback and email) he sent me an Ebay message saying "Before I leave feedback, I wanted to discuss this issue with you..." to which I responded that he ought to send me a picture of what he feels is a problem, which he won't.

What's the deal here? And why can't I leave him negative feedback?