The firing range i go to in Michigan permits CCW holders to exercise their privledges at the facility. However, there is a local firearms store with a sign posted on the building near the entrance that states to the effect: any person carrying a firearm not encased while entering this store will be considered part of an armed robbery!!
I've been to a few gun stores that had "no packing" or similar signs, but nothing as severe as the store in your area. Sounds like the kind of store I would stay away from and encourage others to avoid as well.
There are a couple of stores here in PRHI that require LEO to disarm unless they're at the store on official business. IMO having any law abiding citizen or LEO disarm is VERY BAD for business. I can understand policies of no carrying uncased firearms off of the firing line as muzzle control can be challenging, however a properly holstered pistol shouldn't be a problem.