for the sexually immoral, for homosexuals, for slave-traders, for liars, for perjurers, and for any other thing contrary to the sound doctrine;

 There are the undisciplined (anupotaktoi, G506) . They are the unruly and the insubordinate, those who refuse to obey any authority. They are like soldiers who mutinously disobey the word of command. They are either too proud or too unbridled to accept any control. 