From the article
"Davenport(employee) says that he didn't refuse Martin(officer) service, but he was so busy he had to ask his manager for help. He said that is when the manager made the unfortunate joke."
This is all on the manager, and yes he(manager) should be disciplined (but not lose his job, it's called a warning unless if he's had prior pranks on his record, then I would suspend or possibly terminate depending on # of infractions) and you can eat at Arby's if you like or not.....
on edit:
Of course with the public reaction, Arby's may take a different route.