The name Satan means accuser. The word for devil is related to the word for slander. The devil is the accuser of the brethren; he accuses day and night. When the sons of God were gathering in the presence of God, God bragged on His servant Job, and Satan was the one who accused him of false motives.
We call Jesus by the name Jesus because He will save His people from their sins. Jesus is an Advocate for us, a defense attorney. And He is not an advocate for the innocent. “And if any man sin, we have an advocate with the Father,Jesus Christ the Righteous” (1 John 2:1). Note that it is righteous for God to defend those who have sinned in this fashion. Jesus is Immanuel, God with us. He was born of a woman, born under law, so that those living in darkness could see a great light. He became incarnate so that we might have comfort. And when Jesus was preparing His disciples for His time of departure, He promised them that He would send the Holy Spirit as His own replacement. The Holy Spirit is called the Comforter, the Encourager, the Paraclete.
There is a chasm between these two mentalities. The chasm is so great that once we begin to understand it, we need to begin assembling careful arguments from Scripture to allow for a Christian to serve as a prosecutor or “accuser.” There are such arguments, and there is an appropriate or godly way to fill such necessary roles in our society. We do have a need for prosecuting attorneys. But we need to know where the warnings are. It is like wealth. The Bible has a tremendous amount to say on the subject of wealth, and much of it consists of warnings. It is lawful to have wealth, but watch yourself. It is lawful, in a similar way, to become an accuser. But if a man does, he has to know that he is stepping into a role that appears to have stumbled the devil himself.
I have said a number of times and in different ways that Christians need to learn how to repent of their virtues. Our vices are easy enough to identify as displeasing to God. But our virtues really get underfoot. This is one of them. Righteous indignation is one of the besetting sins of those who believe themselves to be moral when they are merely moralistic. This is why Jesus said that a time would come when those viciously attacking the church would believe that they were doing a service to God. The mentality of the persecutor is one of serene self-confidence because it is self-evident to him that sin must always be accused. But for those who are thinking biblically, sin makes us think of our need for a Savior, a Defender, an Advocate.
Another way of saying all this is that the Christian faith declares to the world salvation by grace. A zeal for the grace of God, Scripture teaches, is a zeal for righteousness. If we confess our sins, John says, God is faithful and just to forgive us our sins. This is a righteousness that goes all the way down to bedrock. In stark contrast to this, the Bible teaches us to see the righteousness of the muckraker as a tin sheet righteouness, nailed in a cock-eyed way to the dilapidated shed of self-improvement.