Rentali

The Rentali were a humanoid race. They had more fingers than humans, and their skin could change color between purple and green.

Around the 17th century, the Thazkans came to their planet and started mass killings of the populace. They were eventually driven away when the inhabitants of other planets realized they would be next.

A millennium later, there was a movement by the Thazkans denying that the Rentali holocaust had ever happened. Negative public reaction limited their influence, resulting in history not repeating itself. (PROSE: Denial)