How is the conscience of all firemen protected in Fahrenheit 451?

From the text:

The police went first and adhesive-taped the victim's mouth and bandaged him off into their glittering beetle cars, so when you arrived you found an empty house. You weren't hurting anyone, you were hurting only things! And since things really couldn't be hurt, since things felt nothing, and things don't scream or whimper, as this woman might begin to scream and cry out, there was nothing to tease your conscience later.