What effect will such a sign have on the likelihood of an armed robber targeting that store?
What effect will such a sign have on the likelihood of an anti-gun liberal shopping at that store?
What effect will such a sign have on the likelihood of a pro-gun conservative shopping at that store?
My guess is that those signs will have almost no positives in terms of deterring robbers or attracting liberal customers. My guess is that roughly 10% of shoppers would never enter such a store, whether or not they personally carry. I would love for every liberal store owner to follow the mayopr’s advice and try it.
I think the effect is obvious. The robber will take one look at the sign and say: "Darn! What rotten luck - this store is a gun free zone!" He'll then turn around, continue on his way, and look for a store with no such sign.
(Yes, I'm being sarcastic.)