Parents and teachers tell children that sticks and stones may break their bones but names will never harm them. Most children intuit that the adults are speaking nonsense: names and other nasty words hurt.
When not consoling children, most adults recognize that acts of cruelty are routinely perpetrated by means of ugly utterances that can sear and scorch, inflicting wounds and leaving scars. The larger truth underlying the deceptive bromide is that while the law in a free society prohibits deliberate harm to property and body, commitment to liberty of thought and discussion generally restrains states from shielding citizens from emotional harms speech can inflict.