What can be said that hasn't already been?
It's unfortunate that there are some people that would rather rattle sabers than first seek alternative solutions. How many time I've seen people complain about an employee on line to everyone without even so much as giving the manager a chance to rectify things.
Example:
Someone on here had a problem with what I once said, and contacted me through PM. He could have gone on the board openly about his/her grievance, but he instead gave me a chance to clear things up.
My very first on line sale (not ebay) was a problem customer, and I recognized it right away (even the postal employee told me they'd had too many problems with him). It was my fault as I transposed the zip code, and the package was sent to a post office six miles from his house, and as a result didn't go direct to him. After a couple weeks, I was able to resolve things and get him his package, but not after he continued to trash me on an open board, in spite of my efforts to make things right by trying to track down the package and get it to him. After getting my package he was all praises.
I could have lodged a legitimate complaint through the proper channels as he had violated the rules of the board with his actions. However, I decided to take the high road figuring that everyone would realize what was really going on.
I sent him his money back, and didn't say anything to anyone about it. Two weeks later I contacted him to make sure he got it (he could have at least said something to let me know he got it since he didn't even know or ask for a refund).
They used to allow responses by the seller. If they still do, you could post something alluding to your statements about desiring to make things right for him. You probably won't be able to (some people are never pleased), but then again, most people with probably see his comments for what they are.