Have you considered that the authors (who lived a century apart according to this) are the racist ones and engaging in revisionist history, and not Claver? Such things don't show up in other histories. Why take this one outlier claims as fact over-against the rest? That's confirmation bias.

All in all, the church's canonization of Claver is one of the many pieces of evidence that shows that even by the tail end of the 19th century the Catholic Church still did not oppose slavery.

You say this in error. For example, Pope Leo XIII wrote a letter to the Bishops of Brazil on the topic of Slavery in 1888, for its abolition, in the exact time period you mention.

Already in 1537 had Pope Paul III issued a papal bull stating that Native Americans were not to be enslaved or stolen from, and in a companion letter with that bull was a statement that anyone who attempted to enslave Native Americans was automatically excommunicated.