They bring up the point that humans are indeed human, and will always have an aspect of humanity inside them no matter what you do. But some people have lost their grip on humanity. Just as dogs are trained to become more domestic and learn to do certain things, humans can be learn evil things and be taught how to live in such a way that others are hurt without the thought of how scary and violent they have become. In the book Monster for example, characters Bobo Evans and James King brutally robbed a corner store and murdered its owner, with no remorse which is shown when they use the stolen money to go eat a meal from a nearby fast food