It can be both a blessing and a curse to do business on eBay. It can give one access to a larger market than one would otherwise be able to reach, but that larger market will also include a few more idiots, and the costs associated with dealing with them.

When I run into the occasional clunker, I sometimes evaluate things to see if there's a way I might have avoided that clunker without having too serious a negative impact on other, generally profitable business. More often than not, my evaluation is that the clunker is just part of the good business. Sometimes I find ways I can tweak things that might avoid certain problems in the future - but I know I can't idiot-proof everything.

I expect you know all of that already, of course - which is why you aren't calling the guy a moron.