In a fallen and imperfect world, a large part of the human family is deterred from exploiting and abusing each other only because of the legal restraints imposed on them by society. Contrary to the false and simplistic claim that "you can't legislate morality" the laws of the land do define morality for most people. Law-abiding citizens consider themselves the good people while lawbreakers are punished as criminals.
And in a self-described "God-fearing" nation, civil law is assumed to complement the rules that have been given by divine fiat. It was this linking together of the sacred and the secular that allowed slavery to flourish.
In order to justify the owning of slaves, people claimed a biblical basis for the unjust laws they had enacted. They did this by perverting the intent of the scriptures and misrepresenting the nature of God. And because they had given themselves a biblical/legal basis for what they were doing, religious people and their clergymen maintained an unwavering belief in their own goodness and piety even as they bought, sold, exploited, and abused other human beings.
As long as human beings go on shedding the blood of animals, there will never be any peace. There is only one little step from killing animals to creating gas chambers a la Hitler and concentration camps a la Stalin. There will be no justice as long as man will stand with a knife or a gun and destroy those who are weaker than he is.
Isaac Bashevis Singer, Nobel Prize winner
The same tactics that allowed pious people to justify a cruel and ungodly dominion over human beings are now used to maintain a brutal and deadly dominion over other beings. Animals are tortured and killed for a variety of recreational, "scientific" and dietary reasons, most of which are legal. And those who commit these legalized atrocities are celebrated as sportsmen and humanitarians.
But at the same time that we glorify hunting, vivisection, and factory farming, we deplore the violence and callousness that increasingly marks the way in which human beings treat each other. And we try to solve the problem of societal violence in various ways. Religion, psychology, the behavioral sciences and penal institutions offer a variety of solutions—none of which have been able to solve this problem.
As long as we brutalize and murder other creatures in the name of God, of humanity, of economic gain, or recreation, we will continue to reap the violence of these actions in our own lives. "Be not deceived; God is not mocked: for whatsoever a man soweth, that also shall he reap." (Galatians 6:7)