You're bolder than I as I tip-toed around the buyers story.
I'm not challenging the op position at all. The subjective part is we hear one perspective. We are not privy to all sorts of details. With that it is difficult to lay out a path to resolution.
The middle road typically is the less messy one regardless of the situation.
It is quite simple, to me.
The buyer had an inspector of his choice look at it. The buyer bought it without any complaint. Now the buyer is wanting a refund of some sort. The time for negotiating the price was before cash was exchanged.
F-off would be my response.
