Disciplining Another Person's Child

How is it that parents can allow their kids to throw chips all over the floor of a restaurant and spit coke at one another through a straw--hitting someone nearby (in this case, me) without disciplining them? It got so bad that I finally went over to the table (with my cola-hair, thank you very much), and politely asked the children who were seated with their parents to please stop spraying me with their drink. Would you believe that the so-called grownups actually gave ME the evil eye? Disciplining your child is hard enough, but disciplining another person's child is enough to turn even a strong parent into an emotional wreck. Then again, no one deserves cola-sprayed hair when eating out.