It is indeed, and not just Tintin in Congo, but as you say its racists elements come from the historical background the author was working on and not because He

It is indeed, and not just Tintin in Congo, but as you say its racists elements come from the historical background the author was working on and not because Hergé was trying to promote racist views (except for Tintin in Congo BTW, because it was ordered by a very conservative editor as a propaganda work, like Hergé's first book Tintin chez les Soviets).