It is normal and apporiate for kids to be afraid of the dark, it can be forgiven. What cannot be forgiven, according to Plato here, are men who cannot face the light. Men are supposed to be the heads of the family, society, organizations and nations. They are supposed to lead and protect. One who leads and protects is one who has seen the light and is not afraid of the beam. They are the ones that are bold enough to do things and answer to their responsibilities.