The cause of evil is ignorance. Because people do not know why their wrong words and actions are not good, they do. There is a saying that falsehood is bad. However, they speaks and acts wrongly in order to escape the crisis they face for the moment, or to satisfy their desires (desire for honor, earthly desires, appetite, sexual desire, desire for sleep).
Words and actions do not disappear for no reason. Just as a handful of air or a bite of food remains in the body, words and actions remain in the consciousness. In addition, words and actions change the consciousness (spirit), just as the quality of air and food changes the physical constitution.
Falsehood once committed leads to another. The lies plant other lies or leave grudges against others. Evil already committed does not disappear by the punishment through the ethics or the law created by the human society or by the forgiveness of the victims. It remains as clear as an indelible wound.
If you point out their lies to false people, they get angry or even make retaliatory attacks. There is a saying that if you point out the wrongness about robbery in front of robbers, you could be attacked or killed. Some of mankind's teachers were also killed because they pointed out the hypocrisy in front of the contemporary hypocrites. Those hypocrites never knew their hypocrisy. It was because the cause of evil is ignorance.