A boarding facility is a business, just like any other. They should be concerned about you taking your business elsewhere. Treating ANYONE like that is rude and inexcusable, not to mention to someone whose business you are attempting to earn. Many boarding facilities believe that once you move your horses in, they can treat you however they want, but I for one won't hesitate to move my horses if someone treats me like that.
Get your girl out of there, or talk to the barn OWNER about the attitude this guy gave you. You know your horse, and you know when something isn't right.