PayPal Dispute Process
The bad comes when you have a lot of disputes. PayPal will flag you as suspicious and there is a chance they block you for a time. I've seen a lot of blocked accounts that have bulk amounts of transactions and high % of disputes. That way the system decides whether you do something bad or you use the system just to transfer your money while you don't sell any service or a product. This guy is a douche. What he thought when he knows his site is in the black list?
The best advice are above. Be descriptive, attach as much proofs as you can, so they can see your arguments. In the future try to avoid unknown people. They don't deserve your attention when it all comes to money. Made a list with all important things the buyers should know, so a user can decide for himself if the product will satisfy you.
And most importantly - use common sense in such situations. Don't be driven by the emotions, it was never a right solution for the problems.