Malachi 4:1

For behold, the day is coming, burning like a furnace, and all the arrogant (proud, self-righteous, haughty), and every evildoer shall be stubble; and the day that is coming shall set them on fire,” says the Lord of hosts, “so that it will leave them neither root nor branch.

Sin blinds people to what is right and wrong.  Sin will justify an error so that repentance is delayed or dismissed by the sinner.  The bible calls it a seared consciousness, so we must pray for those we know are in sin.  We must pray that their eyes open, so they repent and return to God; otherwise, they will not see or react to the stop signs.