I actually don't doubt the Daily Mail about this particular story. Mining abuses in Africa include some of the worst crimes committed by Western civilization (vide: the concept of "Western Civilization" may be outdated), over things some of us in technology would consider essentially valueless today.
Chocolate is almost as serious a concern as cobalt and diamond. The legacy of colonialism created a food and infrastructure vacuum in Africa which is typically filled by mineral extraction and labor exploitation.
