Abraham probably thought there were more righteous people in Sodom and Gomorrah than there were (see study note on 19:14). Concerned for them, he made a legal appeal to the Lord based on God's justice. His prayer might seem bold, as if he were negotiating with God. But he approached God with true humility and respect. He did not try to convince God to act against his will. Instead, he prayed for the well-being of others (compare with Lot’s prayer, 19:18–23).
God is a fair judge. "Righteousness exalts a nation" (Proverbs 14:34). Righteous people help preserve society (compare Matthew 5:13).