His range his rules.
Your money, your right to spend it at a range that isn't anti gun.

Like i said. Get as many people you know to make it a point to tell him that they will be spending their money else where because of his anti gun policy and make sure they let him know why they won't be spending money with him.

I would be posting ads in Craigs list, talking about his shop on forums, Facebook postings, Myspace postings, calling my buddies urging them not to patron his range, talking about his range at other gun shops, etc... etc...