Capitalism precisely precludes slavery. One of the most important and foundational of its principles is private property. The first, most natural, and universal instance of private property is the ownership of one's own body. Heck, we even have the phrase "private parts." Slavery requires the most basic violation of bodily autonomy. In other words, to permit slavery is to permit the violation of the most basic property right. I struggle to see how slavery could be compatible with capitalism.
Is this supposed to be ... a gotcha? If slavery is involved, it's not capitalism, by definition. Distance attenuates all signals, so each transaction step may somewhat smear or smudge such a stain. Really not clear at all what you're getting at.
you assume that capitalism implies that everyone gets to participate. but that is not a necessary condition. you can have a capitalist system where not everyone participates. slaves did not participate in capitalism, but their owners did. one might even argue that employees do not participate in capitalism either (i am not familiar enough with the specific definitions to state that with certainty however).
No! The owners were not participating in capitalism either, precisely because their whole business is predicated on violating private property. If you wish, you can express it as a matter of degree. That by having ones bodily autonomy stripped, one is engaged less capitalistically, and the same for those which strip that autonomy. The violation taints both ways.
What part of capitalism precludes violating other peoples rights or property? By your definition much of US business isn't capitalist because of the prevalence of wage theft and rights violations, which is absurd.