There are literal ledgers filled with transitions showing how Europeans traded with African tribes to receive slaves that said tribes took as PoW. However, all this is ignored in favor of pushing the idea that white people went into the rainforest with nets to "bag me a darkie". They also love to push the idea of slavery started with America and ended with the Civil War (which is funny considering that Vermont and Kentucky were allowed to continue practice slavery until the passing of the 13th)