Amos says that the people went to Bethel bearing abundant rebellions on their consciences, but they returned with them still there. Outwardly, they sinned because inwardly was a heart of rebellion. There was not any real concern about the rebellion in them.
If they had really sought God, they would begin to do something about these sins, their rebellions. A person who is really seeking God is so concerned about having God's approval that he will pay any price, make any sacrifice necessary to stop sinning and thus have His approval. These people did not care. They went right on sinning.
He shows them returning from Bethel unconcerned with what people were in their character (whether they were just or upright), but they were concerned about what they had and what they were prepared to pay as a bribe. This is the gist of, "You afflict the just and you take bribes." The poor person who was telling the truth had no chance in court unless he was willing to pay a bribe to those who were judging him.
These people were not concerned with morals or ethics but how much money, influence, and status they and others had so that they could use one another to get ahead.
John W. Ritenbaugh
Prayer and Seeking God