How might the Portuguese textbook influence, and how it portrayed the Middle Passage?

The Portuguese textbook is a tool to teach students about history. Document A, specifically deals with African slave trade. The first focus of this document is the benefit of the slave trade to African societies, the fact that this trade was just as beneficial to the Africans, who sold their own people, as it was to the Europeans, who increased trade by trading merchandise for what the Africans offered.... their own people. It also makes mention of the negative consequences to slave trade but not in the way we'd expect. Focus is placed upon the danger and difficulties for both the traders and the slaves.

In my opinion, the article is meant to influence the reader to focus on the atrocities of the African lords rather than the European traders. What do you think?