One of our board members drafted this email that was sent to the headquarters of the grocery store from which they generally purchase. Please feel free to use this as a template for your own letter or email to the store(s) who have recently decided law-abiding citizens should not be allowed to protect themselves or their families using their preferred method of protection. You will need to modify it somewhat for your own purposes since it does mention being a board member...but you could easily replace "where I serve as a Board member" with "of which I am a member."
Our family spends approximately <dollars> a week at your store on <location>. Since you have decided to insult your customers with your new policy on firearms that business will now go to one of your competitors. We have a choice in where we shop and your political views are an unwelcome feature of your services. Be assured that I will be sharing my opinion with others including our state Second Amendment organization where I serve as a Board member. Perhaps you can afford to lose the business, but I have always understood that the grocery business was quite competitive with thin margins. We shall see.