Whoever is responsible for that sign should severely pay. Along with jail time if the owner, they should lose their franchise. If the manager or someone else, they should lose their job. If Popeyes doesn't do anything, I have eaten my last meal there and it's my favorite fast food chicken place (love the spicy chicken!).
Can you imagine the outcry if there was a sign that stated "Will reserve the right to REFUSE SERVICE TO BLACK PEOPLE"? If I saw a sign refusing service based on race, I would pass on eating at that establishment.