Because she/he fully internalized what she'd been taught. "Just went a little too far with it."
You've got to be taught to be afraid
Of people whose eyes are oddly made
And people whose skin is a diff'rent shade
You've got to be carefully taught
You've got to be taught before it's too late
Before you are six or seven or eight
To hate all the people your relatives hate
You've got to be carefully taught
— From South Pacific