"Teach slaves to be subject to their masters in everything, to try to please them, not to talk

The evil of slavery is not directly addressed in this verse. That was to come later as the wider implications of the gospel dawned on the early disciples. Nevertheless the disfigured human relationship that is slavery, will not be able to withstand the spirit of service to which even slaves are called as Christ's disciples. Even unjust social structures can be brought down--not by disrespect and hostility--but by humility and love for the evildoer.