I don't have a problem with it, and the thing is obviously nobody else did either if you or no other customer said anything to him. He never held it in a threatening manner, and he probably hasn't any weapon since the War. I wouldn't do it myself, but I guess he knew he could get away with it. Is there a policy or sign saying he can't bring in a loaded gun? Maybe it was his carry piece.
"Damn the torpedoes, full speed ahead!" -Admiral Farragut @ Battle of Mobile Bay 05AUG1864