So were "your people", Motley. Enslavement of one kind or another has been an element of human civilization in every culture since at least the Bronze age. Cities required intensive agriculture which required slaves. Mining and quarrying required slaves. Monumental architecture required slaves. Navigation required slaves.

Furthermore, since you can't know whether anyone's remote ancestor sold humans into slavery (and that includes any of your remote ancestors) there is no purpose in making that unprovable accusation except as an insult.