The Anti-Slavery Slave Specie

 Outlawing slavery and killing slavers makes exactly as much sense as outlawing hair and killing barbers.

 Slavery is an inborn trait. Something you are, not something that happens to you. If slavery is to be stamped out, it is the slaves who must be executed.
 If this seems immorally cruel to you, then you are pro-slavery. 

 "We killed all the barbers and imprisoned anyone who forged razors or scissors. Why is everyone so hairy?"

 

 [Victim] is a kind of person, not a kind of circumstance. Prey is a kind of person.
 What do we learn from the cycle of violence? Those who commit are those against whom it was committed. You can't con an honest man; security is affordable; those who are deviated against are the deviants. Traitors are the ones being betrayed. Criminals are a kind of prey. Going el salvador works because it persecutes the greatest victims.
 Demand draws forth supply. To eradicate the supply of victimization, the demand for victimization must be deleted. Victims must be extirpated. Criminals are a kind of prey, and prey are a kind of criminal.

 Indeed, perhaps that is the solution to the el salvador mystery. Crime got so high that all non-gang victims were slain, resulting in collapse of demand, and consequently collapse of crime.  

 Turns out, when satan demanded a child sacrifice, it was because that child would have grown up to be a deviant, a defector, a traitor. You can't con an honest man, and as always, evil is self-destructive. Satan could never bother truly decent folk, despite desperate efforts.

 Agricultural societies are all slave societies. Farming races are slave races. Perhaps the great filter is wheat and rice. If you fail to reject the tax man, then your species is doomed.
 To de-agriculturalize the species at this point would take unfathomably drastic action, orders of magnitude beyond that which mortals have ever been capable of. 

 I've said before that war crimes are the table stakes. Geneva violations are the door charge. Quite possibly this is softballing the issue.
 The minimum is being able and willing to deliberately speciate. To consciously, strategically forbid cross-breeding. To have Darwin-level power.