Nuclear war is a threat that could lead to the end of the world. If an EMP was used to destroy all electrical devices on Earth, Nuclear warheads would be disabled and weapons could no longer be create, ending the possibility of a third world war.
Animals kill others to survive, humans do it through greed, jealousy and on occasion, fun. Humanity is flawed.
Yes it would take us back eras of advancements, but when you've prevented the possibility of someone starting the destruction of the entire planet, yoyd be greatful it happened.