I sold my 1970 ES-335 on ebay. The highest bidder was somewhere in the middle east, although I explicitly stated in a number of places that I would ship only to the US or Canada. No overseas shipping, etc.
Anyway, I wrote this guy and figured, if he was nice and could explain the situation, maybe I'd consider shipping it overseas after all. But he never wrote me back. So a few days later I wrote another email that said, 'hey I'm just trying to figure out what's going on, please write back' and then, nothing still.
Finally, over a week later I wrote him and told him that since he didn't read the listing fully and that he had never written me back I had no choice but to fully cancel the sale, and leave him negative feedback. This time I got a reply within minutes - accusing me of being a racist! With quite a bit of vulgar language and imagery thrown in to boot.
Like others have said, you set the rules for the transaction, not them. By bidding on and winning at item, they implicitly agree to your rules. If they won't play nice, cancel the deal and leave them negative feedback.
They're the ones who make the most noise also. Makes the rest of us feel like we're outnumbered, but the news isn't full of happy endings so we don't hear about the honest people.
And people wonder why I'm antisocial