Herge's Tintin In The Congo published in 1931 has a well-deserved reputation for a stereotypical, colonialist and racist viewpoint of the Congolese native population as part of the Belgian Empire So much so that even Herge would revisit it and re-edit it to make it not quite so much on the nose, during his lifetime[...]
Tintin in the Congo Archives
Which suggests he must've been reading Tintin in the Congo, an early book in the series and one that would later spark controversy for portraying racism, as creator Hergé has long been accused of.
It even infamously spawned a 2012 court case, during which a Belgian court ruled that the 1946 edition of the book did[...]