The simple sign reads: "NO CONCEALED WEAPONS ALLOWED. If you are such a loser that you feel a need to carry a gun with you when you go out, I do not want your business. Douchebag."
Personally, I can't tell if he's calling gun owners Douchebags or if he's signing the letter and his name is Douchebag. I prefer to go with the assumption that his name is Douchebag. At the very least, he'll always be a Douchebag to me.
If you want to let them know your thoughts on this, feel free to call owner Peter Matsko at (864) 653-7581. This is the restaurant's public number as we would never disseminate private information on any person.
Oh, and a pic of the sign just for good measure: