It doesn't matter what you say, he'll never change his position. Its not about cables, its about him being right. Give him all the proof you want, and he'll come up some excuse, no matter how small, to invalidate whatever it is you show him. Here's an example.
Gorquin. Here's a white paper on Audioquest's DBS system. It goes over what break in is, and what it is not. You'll also see the patent number AQ has on this system.
http://www.audioquest.com/wp-content/uploads/2011/12/DBS.pdf