You can't argue with stupid and will most likely never be able to make this customer happy. Seems like he's acting in bad faith so I wouldn't bother reimbursing him if I were you, as long as it doesn't result in monetary loss for your business in the long run (IE, negative feedback left that would influence potential buyers, trash talking on forums, etc.). This is one of the few reasons why some Amazon/eBay sellers don't argue with picky customers and often fully reimburse them without even asking for the broken/defective product back.