Hiram,
I think you should send him a letter, not because you are being a nice guy, but because you want to rub it in a little. Right now he is thinking that he stopped the other shop from spying on him, and it makes him feel good. Will he still feel good when he finds out what he really did, that he drove away a very good customer, and make sure you tell him exactly how much you have spent in his shop and that you will never enter his shop again. You can not actually give him a kick in the ass but you can make him want to give himself a kick in the ass. He who laughs last.
A friend of the family did something similar to a car dealer. He always bought a new Cadillac every two years, once when he went into a dealer to purchase a new car, he was dressed in work clothes and the salesmen paid no attention to him because he did not look like he could afford a new Cadillac. Well he got ticked off and left and went to another dealer where he was treated right and he purchased his car. A few days later he returned to the first dealer but this time wearing a suit, so guess what a salesman immediately asked what he could do for him and he asked him to step outside where he showed him his new car and told him where he bought it and why and that he was going to purchase his next car from the other dealer. The salesman was not very happy about losing the commission.
So send him a letter and rub it in real good.
There is a shop in my area that also has the wrong attitude. This shop was just taken over by a new owner who is related to the previous one and he has a bad attitude toward his customers. It is not that he treats them bad in his shop but that he feels that since he owns the shop he can come and go as he pleases. He is supposed to close at 6:00 which is what it states on the door but he is almost never there until 6:00. Sometimes he closes at 5:30 other times at 5:00 or even 4:30 or worse yet never even bothers to open. I used to go there all the time but now I go to another shop. I got tired of going there to get something and finding him not open. I was even going to give him some freeware and shareware for the computer he just installed and help properly set his system up. But every time I went there he was closed, I tried calling him early in the day with no luck, even one of my friends thought he had closed up. Well I finally found him open one day and I asked him what happened and he told me that he had a life and had other things to do other then be in the shop all the time. I told him that he should have at least put a note on the door that he was not going to be open his normal hours so people would not come to his shop for nothing. He even stated that it was his shop and he did not have to explain anything to anyone and if someone did not like it they could go elsewhere. Well I have decided to go elsewhere.
There is also another shop that is now closed where the owner told a very good customer to leave simply because this customers friend was in the shop and going to trade a pistol for something and he told his friend that he should keep the pistol and just purchase the item he was interested in. I guess the dealer really wanted that pistol since he got very angry and ordered his soon to be ex good customer out and not to come back. And this customer had spent several thousand in his shop in the last few months, and was his best customer.