The problem is that the judges of this world are not living as judges. They are not directed by the Most High, but are directed by their own foolishness.
The reason Christ told the people: he that is without sin, cast the first stone, he was showing them that all of them deserve judgment for one thing or the other. He displayed how society has gone so far from Jah, that they have no right to bring any judgements from Jah. And as Christ showed in another part. He who forgives, will be forgiven by Jah, he who shows mercy, will be shown mercy from Jah. And also the parable of the man who owed a debt to another, but was unable to pay, and his Master forgave him, and allowed him more time. But then this same man went to someone who owed him money, and didn't give him the same allowance, but treated the person badly. When the Master saw this, he was wroth.
Jah showed mercy to all the people that committed their sin, so Christ was showing that they should also show mercy to others. Adultery is wickedness, but it is not the worse thing that people do. Christ didn't punish this woman, but look at what Christ did to the money changers in the temple. He drove them out with a whip, and turned over their money containers and tables. There was much more serious wickedness going on in the high places of Jerusalem that Christ came to battle. He would rather that the sinners, like the woman, turn to Jah and sin no more. He did not leave the woman alone, he gave her this judgement:
10 When Jesus had lifted up himself, and saw none but the woman, he said unto her, Woman, where are those thine accusers? hath no man condemned thee?
11 She said, No man, Lord. And Jesus said unto her, Neither do I condemn thee: go, and sin no more.
12 Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.
Jah forgives the sins of the past, and they will be remembered no more for all that turn unto Jah in righteousness. This is not a new thing, but was from the beginning and was also spoken of in the Old Testament.
In these times, I and I should judge our own actions and thoughts, and not tolerate wickedness from I and I self. If your hand offends against you, cut it off. Burn Fire on any wicked thought or action. Because it is better to burn Fire on yourself now, while you are living, then to die in wickedness, and burn eternally, where the worm dieth not, and the Fire is not quenched. Salt is Fire, and Fire is good, so have Fire within yourself, and cleanse yourself unto Jah.
And here the instructions Jah give to the judges.
Addressing Judges on Justice and The Law
Haile Selassie I