Slaves are better off dead than toiling in the razor cardamine fields of Malta.
Or, just RP that you didn't blow them up, you disabled them and boarded and moved all the slaves away on police/military/allied transports (who happen to be NPCs). It just looked like you blew up the ship, due to game function limitations.
Just don't RP arresting the slaver(s) after boarding their ship, since that's pretty hard godmoding. They escaped on escape pods, as usual.
Then the ship was scrapped once the slaves were safely freed.