Actually they did kill halfbreeds - that's why D'Argo's wife had to hide the existance of her son - her brother never knew there was a son or he'd have been the first to kill him. Jothee would easily have been shot by, say Bracca, if Scorpius hadn't held him under his protection. Typically, I'd guess, they are killed as babies/children, adults are more of different problem.
The enslavement of other races was mentioned time and time again thru out the series, and was an ongoing theme. Zhaan, in fact, had murdered her lover because he betrayed their planet to Peacekeepers, hiring them to extend his rule beyond 10 cycles, increasing his own power while dooming his planet to eventual Peacekeeper control. Rygel mentioned something of a similar problem with his cousin. D'Argo, whose people had successfully fought off Peacekeepers attempts, was horrified at the 'mutual protection' alliance his people were signing with Peacekeepers, he spoke to the delegates and asked them how they could do that when they must know the Peacekeepers would just use it a footstep to gain control (they explained they were not really allowing Peacekeepers anymore power, from their point of view but that's beside the point that Peacekeeprs using alliances as a takeover method was clearly an established history) and even the plant growing people of TGIFAgain were victims of typical Peacekeeper conquering and slavery, unusual only in that they were outside the established terratories.(the bettrer to keep a weapons fuel source a secret)
When Scorpy proposed having Peacekeepers protect the planet Earth, John knew it was a bad idea. He conferred with D'Argo who spelled it out, Peacekeeper protection means slavery. That's what they do. Its the reason they are reviled in both the 'charted' terratories and the Uncharted Terratories, and why Scorpy's own mother was a part of colonist groups seeking places far away from Peacekeepers to start a new life. Even if it meant facing threats unprotected.
The Royal Planets were three planets of sebacians that made it thru to establish a new life and defied both sets of conquerers, by setting one up against the other in a delicate balance that kept their little space a protected "neutral" terratory, so long as each was unready to start a war with the other. The only people more hated on that planet than Scarrens, were Peacekeepers.
Scorpy's commission was a great grand exception in Peacekeepers policy on halfbreeds, and it was indeed because he was the ultimate halfbreed - someone genetically half of their greatest enemy, offering to share a wealth of secrets to them if they'd just open their doors. The unusually open minded captain of that ship (I always imagined him conscripted .. and he smiled! did you see that? smiled! .. of course Wayne said a lot of what Scorpy said was truth bent to fantasy to convince John of his good nature, the truth was probably closer to a blackmail scheme, but same intentions of learnng what they could) saw a grand opportunity to be exploited and took it, while lesser officers would have gladly shot the creature where he stood.
....
as for John Crichton - oh, he went far beyond the morally good when he dropped that nuclear bomb in Katrazi - that was a much a terrorist act as anyone could ever have, in our world - and the impact wasnt any less on the Scarrens. John knew it and so he cried ..... but it really didnt make him a better person.
The wormhole weapon was a more extreme of the case ... I dont think John acted the hero in either occaision .. but the story is written so that its about his events, his character, his point of view, and it was very dramatic and heartwrenching to see our nearly pacifist young astronaut become this in a mere 4 years. That's the story, as much as anything, and about how he and Aeryn come together.
But John playing the devil never excuses Scorpy from the role for me - besides, Scorpy plays the bad guy so deliciously, I'd hate to see him compromised and do good someday, on purpose.
