I think the admonition about the character of the gospel as light is also applicable to the second type of men. He made analogies that men don't buy or trade in the dark or do their daily work in the dark. Cheating too is done in the dark, as are all the evil works of men. And that is why we need light, for it makes us safe and comfortable, and this is exactly the work of saving grace. Grace turns men from darkness to light and exposes the works of darkness.