These passages all have a similar context: They were written just prior to the fall and scattering of either Israel to the north or Judah to the south. Each shows a wealthy people unblinkingly focused on their pleasure. Giving no thought to God, they are casually uninterested in the moral welfare of their nation that is crashing into utter depravity. Shame for sin has disappeared. The Interpreter's Commentary of the Bible states that the Bible shows that, in the period before these nations fell, their societies show significant breakdowns in two vital areas: in political and business leadership and in family life, with specific blame falling on women.
In these passages, the following characteristics are either directly named or strongly implied: rebellion, obstinacy, betrayal, distrust, shamelessness, and greed, comprising an audacious self-centeredness against God and fellow man. These are not the characteristics of a nation that would bring honor to God. At one time in the history of this nation, the overwhelming majority of people expressed a strong sense of shame when they sinned. Sin was an ugly thing, and due to this sense of shame, they did whatever they could to hide their moral flaws from others.
Some of that still exists. The period of the late 1950s and early 1960s, however, was probably the beginning of the end of that attitude. Sin has gradually carried less of a stigma, and the sense of shame has been slowly replaced by a growing boldness of attitude, a flaunting of sin. Much of that sense of shame has disappeared from the American psyche. Some remains in a small percentage of the population, yet increasingly, bold immorality has become the way of life so that sin is now blatantly committed. Civility is becoming a thing of the past. Rudeness and open, brazen misconduct is becoming the normal way of doing things.
This is the kind of conduct the "whore's forehead" pictures. It represents the blatant, audacious sin of the streetwalker who is out in public, openly displaying what she is, promoting herself, and tempting others to engage in sin with her. The whore's forehead represents obdurate practice of sin done overtly with no attempt to camouflage. This attitude is reminiscent of the story of righteous Lot dealing with the homosexuals in Sodom just before God dropped the fire and brimstone on the people of that vile city (Genesis 19).
This relaxed and careless public acceptability of sin did not happen overnight. It gradually became tolerated over decades. Its growth was significantly aided by a so-called Christian church that abandoned its responsibility to "cry aloud and spare not" and show God's people their sins (Isaiah 58:1). We must be very careful to guard ourselves from succumbing to the temptation of being drawn into the same casual approach. It is our responsibility to overcome sin.