This assumes that every brain can be hardened to any words that can be thrown at it. The reality is that evolution is an experimenter, some brains can be, some brains cannot be. Toss up.

Other words there are some people you can absolutely drive to madness with pure words, no matter how their parents tried to harden them, or how they've tried to harden themselves. They've just got brains that can be destroyed by certain frequencies, same as those wobbly bridges that can be destroyed by certain frequencies. It's an engineering issue.

And there are people you cannot harm at all with words, even though their parents didn't really do much to harden them at all.

Goes for kids too of course, some kids are just born rock hard.

Sometimes feels like we've forgotten how evolution works, and developed this goofy idea that you can just "parent away" any genetic default that you want to. It's as silly as saying you can parent away a peanut allergy.