There is no moral decision which leaves us unchanged. This is an encouraging thing. Such a callous disregard of life, indicates a movement well along the continuum towards complete depravity. Most people will, thank God, never fall so far. This is the dynamic of moral choice.
Conscience is one of the human person's most delicate organs.
I like to compare it with the eyes, in terms of its delicacy. Working with an electric arc welder or even in toxic fumes can, unprotected, cause irreparable harm to the eyes. Like the eyes, if it is damaged by bad choices, it will gradually lose its ability to distinguish good from evil. On the other hand, each bad moral decision damages the conscience, making it less able to distinguish what is good from what is bad. Feeling good Feelings have got a justifiably bad name among many of us in recent years.