What does Isaiah 5:20 mean?

The next "woe" is for those in Israel who see sin and consequences as if looking through a mirror. They have reversed what is evil and what is good. This is one of the many ways of sin. We might engage in sin with the understanding that we are doing something wrong, telling ourselves it is only once or only for a short time. Through this action, the root of that sin begins to grow and we begin to believe the lie. What we once knew as evil becomes normal. To continue to embrace it, we must eventually twist the truth we once knew to convince ourselves that the sin is healthy and right. To maintain our belief in that lie, we must supplant our previous understanding of good with this lie that has taken root. And the sin grows.

Sin doesn't just lie to us. It makes us experts in lying to ourselves. We develop conviction and passion that wrong is right, black is white, and up is down. The modern world is filled with examples of cultures who defend sins condemned in Scripture, while condemning the godliness described in the Bible. When society tolerates evil, that's bad. When society begins defending sins as if they were morally good, and condemning moral goodness as evil, it's a catastrophe (Proverbs 14:34).

The people of Judah and Jerusalem came to see faithfulness to God as an obstacle to personal happiness. His restrictions kept them from gaining the personal success false "gods" promised. The Lord's commands to care for others restricted their comfortable lifestyles. To their eyes, the poor were poor for a reason. They thought it unnatural to upset the order of things by elevating the poor or defending their cause.