I'm going to repeat myself. By your logic a business can discriminate against anyone. Clearly they can't.
Dress codes are internal policies and not laws. There's a clear display of stupidity regarding that code. What exactly constitutes a weapon? I can tell you a bottle of water is, a soda can certainly is, a 4 year old could kill someone with a ball point pen where he couldn't without one. Weapon, Weapon, Weapon.
Your going to have to show me where a backpack is LEGALLY prohibited anywhere.
You can be sued for something you couldn't be prosecuted for.
You can be prosecuted for things you can't be sued for.
Were mixing and matching different legal codes and definitions here.