I think every letter questioning a business gun policy needs to reference Kroger's choice and experience. Kroger has very publicly and firmly announced they will not restrict guns beyond what local laws allow, and their profits went up at the same time when most others in the industry went down. It basically needs to be pointed out that allowing guns will not be TEOTWAWKI, nor will customers desert in droves, or whatever else they worry about. The #gunsense people have even given up on Kroger.
Of course, if the CEO or owner is #gunsense, then it's hopeless.