The Goodness Fallacy Embedded Within Relativism

Quote from Christopher W. Brooks, writing in his book, Urban Apologetics: Why the Gospel is Good News for the City:

"...the goodness fallacy embedded within relativism is the belief  that people are generally good and that we only misbehave when pressured by undesirable scenarios. The logic is that we shouldn't judge our own actions or the actions of others as wrong because we are all simply acting on the best choices available in light of the surrounding factors. This first deficiency is based on the presumption that evil only exists outside of us, an external enemy lurking somewhere in the shadows of our circumstances. This idea, however, couldn't be further from the teachings of Scripture. Consider the words of Jeremiah 17:9: 'The heart is deceitful above all things, and desperately sick; who can understand it?' Christians must reject any system of morality that is built upon the false assumption that people are basically good." Christopher W. Brooks