Words are human claws
Wild animals generally have at least one special defense or weapon that is key to their survival, and defines their ecological niche. Tigers have claws, sharks have teeth, birds can fly, mosquitoes suck blood, turtles have armored backsides, giraffes have long necks, rabbits have acute hearing and extremely fast running reflexes. If a creature that depends on one of those things loses the use of it, they pretty much die.
Humans are a social species. Our niche is our ability to communicate with each other and form communities for mutual protection. That's our special defense. Very few individuals can survive alone for any length of time – and even those who have done so were not born into isolation, but ended up there by accident... and their survival depended heavily on knowledge (and often tools) they received before being stranded.
Words are as important to humans as claws or fangs to a predator, or ears and digging to a rabbit. We can't survive without them.
When words are used to attack, it is as dangerous as a physical fight would be among other animals: this is our survival tool being turned against us. Our lives depend on what we learn from them, the community they create, the mutual understandings they build.
The wounds may be invisible, the deadliness slow and subtle, but nonetheless: words can wound, words can kill.
Anyone who says otherwise is trying to take away your claws, your wings, your shell.