Conscience. You know, that tiny voice inside you telling you not to sneak a cookie when you were a kid; not to say something mean about that girl when you were a teenager. That voice that tells you something different than you want to hear at the moment. The voice that can grow weaker and weaker until it is all but drowned in louder music, another movie, another drink, more clothes, or another car.
What happens to a person whose conscience is dead? They would be someone who uses others, with no thought of the other's rights as a person. The person with a dead conscience would not be hindered by any degree of remorse because they have squelched that voice telling them that everything doesn't exists to serve them and increase their power. They are the Hitlers, the ones that shock us.
And what happens to a nation when the freedom of the Church's conscience, that small voice in our society that says maybe something is wrong with our utilitarian way of thinking, is squelched? Well, we will all be at the disposal of the powerful and what they deem is necessary for the sake of progress. You get things like human experimentation and annihilation; scientists forced to choose between their lives and doing unimaginable experiments on human beings.
Impossible? It has happened before. It is time to be shocked.