The Anomaly of Anti-slavery Legislation

How do we explain the need for government to impose regulations on such an atrocity while protecting free trade? Was William Wilberforce of the English Parliament against free trade by working to abolish slavery in the empire? What is the true role of government in economic enterprise?
This issue brings us back to our discussions regarding private property and the rule of law. It is government's charge to steward the rule of law and protect private property. The issue of slavery abolishment is not an impingement on free trade. It is government's duty to protect private property. Slavery is the most obscene private property violation in human history. Let government lay down its firm hand to abolish it, even if it costs the economy.
I believe the argument in the previous paragraph stands alone sufficient to argue for government intervention in antislavery. However, I would like to propose a hypothesis. If one were to research the archives of economic activity in the West Indies, I believe you would find high cost per unit of sugar production by using slave labor. I suspect that, as my professor, Dr. Howard Baetjer suggested once in a class, that companies utilizing slave labor would suffer from poor productivity. Their prices would not be as competitive as more honorable labor practicing companies. Looking at parliamentary archives would reveal these slave based companies need to protect their product through government regulation. If this were true, I suspect if the regulations favoring the slave based companies were lifted, natural selection would have worked its course. The higher productivity companies utilizing honorable labor practices would have choked out slave based labor. It would have no longer been a viable economic option.