I am going to let other people know that they should take their hats off in a restaurant.
Why does it matter to you if someone has a hat on in a restaurant?
If they don't want their hats to touch my food, then they shouldn't have them in the premises.
You need to mind your own business because it is not your responsibility to tell other people what to do. There is not reason why a person can't wear a hat in a restaurant if they choose to do so.
Why can't I?
You really should not be worried on whether someone has a hat on or not in a restaurant. You are better off just trying to have a good time with the person you are across from.