What does Psalm 82:4 mean?

Money, power, and influence are never evenly distributed. Those in need or weakened need others to advocate on their behalf. A crucial purpose of human government is to restrain the strong from abusing the very weak (Proverbs 31:9; Psalm 72:12–14). When this is inverted, it undoes the basis of all human civilization (Psalm 82:5). This is part of God's command and formal accusation against corrupt judges in Israel (Psalm 82:1–3).

In another psalm associated with Asaph he also mentions the wicked rich oppressing others and bragging about it (Psalm 73:8). Such treatment rejects what God says about treating the poor fairly and with deep compassion (Exodus 22:25–27). An example of this done correctly was King David, who exercised his power on behalf of Mephibosheth, who was lame. Rather than ignore him, or punish him for being part of Saul's family, David was kind. He let Mephibosheth sit at the king's table and gave him servants and property (2 Samuel 9).