Should you refund him in any way? Unquestionably NO!!! Clearly a scammer. If he's being a d_ck to you, be one right back!!
However, you seem to be getting a lot of input here from sellers and most are very biased points of view. Sellers want to maximize their profits, so they feel they never do anything wrong.
If nothing else, you should listen to some of us buyers, too. If you're listing a trimmed card, you need to make it much clearer. It's right there in your auction--in red--so I'm not putting any blame on you. But if I was looking at that auction, I'd be disturbed by the almost complete lack of a description. If it's trimmed, say "This card has obviously been trimmed" in your description.
Oh, and get rid of that Cobb picture.
