My parents were also of the "take the troublesome child outside and Have Words" school of thought. When my boy starts acting up, we stop what we're doing, I kneel so I'm at his eye level, and state quietly, emphatically, that his behaviour is unacceptable and guarantees that he's not going to get [item he's having a tantrum over]. This threat is most effective when we're at Disneyland, because being able to say "I'll take you home and let Nana (his grandmother) watch you for the rest of the day, and I'll come back here and have fun without you" is hardly empty at all - we live 30 miles from the park and I have free parking.

I love my son immensely, and I will not see him turn into a self-absorbed, self-entitled git with no clue on how to behave in public. I loathe children who can't behave in a restaurant, and I absolutely detest the parents which allow that behaviour to continue unchecked.