Let’s see — you put a message on your board that expressed hatred and hostility toward an entire group of people based on the actions of one member of that group, and you are surprised because people are “taking it the wrong way”? In what “way” do you honestly expect people to take this?
If it had been a Christian who committed the mall stabbings, would you have put a message on your board saying, “Christians get out”?
If it had been a Jew who committed the mall stabbings, would you have put a message on your board saying, “Jews get out”?
I hope people avoid your restaurant in droves, as they find places to eat with a far less hateful vibe.