If I were you, I would simply refuse to conduct anymore business with those who have that policy.
My wife and I went to Costco, but before that we purchased a frozen Starbucks drink for the wife, upon attempting to enter, we were stopped and we were given the choice of discarding the drink or leaving it in our car (90° day out)... I selected my own option as said adios... Just because some degenerates leave/spill their drinks in the store, does not mean I will be irresponsible and let it happen.
Same thing with stores with no gun signs, I simply refuse to do business with them, cease to fuel the stupidity with your hard earned money.