Ragdoll kind of has a point - I mean, I disagree that slavers are significantly less bad than the kind of scum they usually work for - and in this case, they kind of have proof that they're also murderers (and if they knew what the reader does...) - but they do regularly agree to work for some pretty high level scum.
On the other hand, even villains usually draw the line somewhere, and (especially given the histories of some of the Six), slavery's as good a place as any. But 'drawing the line somewhere' is kind of the dividing line between your typical villains, and the complete psychos, and we already know which side of the line Raggy sets on.