Every now and then someone will say something like “Despite the fact that slavery was immoral the modern world was build upon slavery and we owe the lifestyle we enjoy to the sacrifice of slaves…” Sounds compelling – except its not true. Slavery held back the advance of civilization because its pointless to innovate, invent or automate when you have (free) slave labour. Absent slavery the agricultural revolution may have begun decades earlier. Slavery was an abomination, and positive ends can never become of corrupt means.
Source: Seeing Not Seen – Slavery did not advance Western Civilisation.