Cruelty, whether physical or emotional, isn't normal. It may signal what psychologists call the dark triad of psychopathic, narcissistic and Machiavellian personality disorders. One out of about every 25 individuals has an antisocial personality disorder. Their prognosis for recovery is zero, their potential for hurting you about 100 percent. So don't assume that a vicious person just had a difficult childhood or a terrible day; most people with awful childhoods end up being empathetic, and most people, even on their worst days, don't seek satisfaction by inflicting pain. When you witness evil, if only the tawdry evil of a conversational stiletto twist, use your ninjutsu, wait for a distraction, then disappear.