Shame on them for causing your problem. Double shame on them for saying it was not their fault. It was, pure and simple. ASE certification my left hind foot. The guy is trying to say he is smarter than the engineer who designed your engine. He’s not. If it calls for five quarts and had at least 1-1/2 quarts more than that, the foam killed your engine.
You may not need to go to court. Just show him these posts. He is outvoted, at least six to one.
See my iffy lube experience posted here about ten months ago here: http://community.cartalk.com/posts/list/2136790.page
I have not needed to go back, but will always remember to check my oil if I do have to.