From John (St. Andrew’s Expositional Commentary) by R.C. Sproul:
All of us, even the most pious Christians among us, are overwhelmingly influenced by the cultural customs and conventions of the societies in which we live. It starts in school, where popularity means “being with it,” that is, being in line with the morality of the society, even if that morality includes things of which God does not approve. That’s what our innate struggle with sin is all about. We listen every day to the voices of the culture around us that tell us what’s politically correct and what isn’t, what is socially acceptable and what isn’t. Then, for a few minutes on Sunday morning, we hear the law of God. We know they don’t match up, but unless or until the Holy Spirit takes the law and pierces our souls with it and convicts us of sin, we don’t really pay attention to it.