They're both douchebags. Selling used cars isn't as easy as dropping the price from the KBB. I had my dad's Buick Century a couple years back, and needed to sell it. It had a KBB value of about $5400, and with only 69K on a 2002, with all records, and an updated stereo, I listed it at $4800 in the local papers. No takers. Put it on craigslist. Got a couple inquiries from local dealers, trying to lowball me (and they weren't really insulting, either). Long story short, after spending about $150 in advertising trying to sell it, I finally got rid of it six months later, to a dealer who gave me $3000 for it. He told me that unless people had financing, they weren't likely to buy from a private seller in my price range.
As far as the seller of the Land Rover, he'd probably had more luck with a higher asking price. Listing at half of value just told potential buyers that there was a problem he didn't want to divulge. Responding to the lowball offer probably just confirmed it, and he didn't even try to negotiate a higher price. I wouldn't buy from the guy, either.