I found this:
**Spanish Slavery vs. English Slavery
The Spanish considered slavery to be an accidental and unnatural condition for humans. They did not believe slavery was hereditary. Both the law of the Catholic Church and the Spanish legal code (the 13th century Siete Partidas of King Alfonso X) treated slaves as humans rather than as property. The Partidas guaranteed protection of slaves from abusive masters or freeman and allowed slaves to testify in court against their masters. Additionally, because the Catholic Church treats marriage as a holy sacrament and views the family unit as sacred, slave owners could not split up a family by sale. A cedula (royal proclamation) of 1526 allowed slaves to purchase their freedom or coartación. Manumission (an owner granting freedom to a slave), while rare, occurred more frequently under Spanish law than British law. Further, unlike the English, the Spanish used white European slaves, so they did not equate slavery with race.
In contrast, the laws of economics had a much greater impact on British-American slavery than the laws of the Anglican Church or English common law. English colonists quickly adopted permanent, hereditary, race-defined slavery. English law defined slaves as commercial property (like the 1856 U.S. Supreme Court’s Dred Scott decision) rather than as humans performing a type of labor. English colonial assemblies passed “Negro Acts” that prohibited slaves from growing food, assembling, earning money, testifying in court, or being educated. Enforcement of slave codes, as well as individual discipline, depended on each slave’s owner and was often arbitrary.
Notwithstanding the contrasting Spanish approach to slavery, Spanish administrators were not entirely color-blind. They segregated militia units based on race. Sentencing records indicate they punished petty criminals of African background more severely than they punished those of Spanish heritage. The life of a slave in colonial Florida was not necessarily better than the life of a British slave in Virginia. However, the institutions of government and church offered Spanish slaves better legal protection and more opportunity for freedom.**
It was at this website:
I believe the Latin Catholic Church also has several saints who were exceptional for their care of slaves.
In any case, it seems the Catholic Church has always been consistent in its teaching on the human person. That is a HUGE difference between the slavery of the United States and slavery in relation to the Catholic Church. But I guess the truth does not really interest anti-Catholics.