This has already been established, the dude is being petty, he even said it himself that what he's doing is petty.
If he's a deadbeat buyer/has buyer's remorse, then he's an ***, but maybe the shoes were really in worse condition than expected? I don't know because I don't have the shoes in my hands. Either way though, yes, the buyer gets honored a refund if they want to if they believe the shoes are not as described. The seller didn't work with the buyer, so the buyer took to his means to get his money back. Your entire narrative is on the belief that the buyer had buyer's remorse, and maybe so, but I don't see how you can certainly draw that conclusion with out a doubt.
If the return is handled properly the seller would've got his money back for selling the item, he may have been out his shipping fees, but it wouldn't be negative 160 or so like it is now. As a long time eBay/Paypal user, I've had to deal with situations like this, and it definitely sucks for the seller, but that's the problems you gotta deal with when using eBay/paypal since it's part of their ToS.