How the fuck do people like this live with themselves?

I recently bought a 3DS on eBay. I had MEANT to buy a "new 3ds" - the 2nd iteration of the system. I realized what I'd done, went back to look at the listing and sure enough, I'd screwed up. Well, that sucked, but hey, my bad, right? So I cleaned it up a bit, I updated the firmware to the latest version, and reset it to factory defaults (because the previous owner's information and pics of their kids were on it). Then I sold it again.

Lucky me, it sold within 90 minutes! Except the money was put on hold because I rarely ever sell anything. So this guy apparently made the same mistake, but instead of manning up and trying to sell it again, this entitled asshole puts in a claim that the item was DEFECTIVE and demands a refund. And because he claimed it was non-functional, it's covered under eBay's guarantee and I can't even turn down the refund. I'm so angry right now.