Revealing one of the most significant themes in Catholic theology, namely, the play between nature and grace, St. Luke tells us that people came to John the Baptist, asking what they should do to reform their lives. John responds with good and very pointed moral advice.
To the tax collectors he says, “Don’t take more money than you ought” and to the soldiers he urges, “Do not practice extortion, do not falsely accuse anyone; be content with your pay.”
In so saying, he was addressing very common practices of that time and place. Tax collectors regularly demanded more money than was just and skimmed the surplus for themselves — which helps to explain why they were so unpopular. And soldiers — young men with weapons and too much time on their hands — predictably acted as bully-boys, extorting money through threats of violence.