Being greatly moved by the deplorable condition of the Indians in Lower America, our illustrious predecessor Benedict XIV pleaded their cause, as you are aware, in most weighty words, in his letter Immensa Pastorum, given on December 22, 1741; and since we also have to deplore in many places almost the same things that he then lamented, we most earnestly recall those letters of his to your memory. For therein, among other things, Pope Benedict complained that although the Apostolic See had done much, and for a long time, to relieve their afflicted fortunes, there were even the "men of the orthodox faith who, as if they had utterly forgotten all sense of the charity poured forth in our hearts by the Holy Ghost, presumed to reduce the wretched Indians, without the light of faith, and even those who had been washed in the laver of regeneration, to servitude, or to sell them as slaves to others, or to deprive them of their property, and to treat them with such inhumanity that they were thus greatly hindered from embracing the Christian faith, and most strongly moved to regard it with abhorrence." It is true that soon afterwards the worst of these indignities - that is to say, slavery, properly so called - was, by the goodness of the merciful God, abolished; and to this public abolition of slavery in Brazil and in other regions the excellent men who governed those Republics were greatly moved and encouraged by the maternal care and insistence of the Church. And we gladly acknowledge that if it had not been for many and great obstacles that stood in the way, their plans would have had far greater success. Nevertheless, though much has thus been done for the Indians, there is much more that still remains to be done. And, indeed, when we consider the crimes and outrages still committed against them, our heart is filled with horror, and we are moved to great compassion for its most unhappy race. For what can be so cruel and so barbarous as to scourge men and brand them with hot iron, often for most trivial causes, often for a mere lust of cruelty; or, having suddenly overthrown them, to slay hundreds or thousands in one unceasing massacre; or to waste villages and districts and slaughter the inhabitants, so that some tribes, as we understand, have become extinct in these last few years?
http://w2.vatican.va/content/pius-x/en/encyclicals/docuмents/hf_p-x_enc_07061912_lacrimabili-statu.html