The Pentateuch is clear on what to do with slave traders who captured anyone to abuse or to sell: they were to be killed. The so-called believers in Jesus who condone slavery of any other man under any false pretense are liars just like Satan whom they serve in reality, unbeknownst to them or not. 

Exodus 21:16 ASV
(16)  And he that stealeth a man, and selleth him, or if he be found in his hand, he shall surely be put to death.

Deuteronomy 24:7 ASV
(7)  If a man be found stealing any of his brethren of the children of Israel, and he deal with him as a slave, or sell him; then that thief shall die: so shalt thou put away the evil from the midst of thee.

The New Testament also condemns 'men stealers' or slave traders

1 Timothy 1:8-11 ASV
(8)  But we know that the law is good, if a man use it lawfully,
(9)  as knowing this, that law is not made for a righteous man, but for the lawless and unruly, for the ungodly and sinners, for the unholy and profane, for murderers of fathers and murderers of mothers, for manslayers,
(10)  for fornicators, for abusers of themselves with men, for menstealers, for liars, for false swearers, and if there be any other thing contrary to the sound doctrine;
(11)  according to the gospel of the glory of the blessed God, which was committed to my trust.