The problem, as I see it, with that sort of communication, is that if you are wrong about a connection between gun bans and store closings, the reader just laughs at you.
Alternatively, the sender seems vindictive. "Haha! You booted us, and now you are closing."
I'm betting the store owners saw business trends and income graphs, and will totally know whether the gun ban was the cause of their problem. From another angle, I'm inclined to think that if the business saw a precipitous drop in business coincident with a gun ban, they would have reversed the policy pretty quick. Business is business.