There are interesting revisionist posts in this topic. Herero genocide is well documented by Prussians. It was even investigated by Prussian Parliament. There were also concentration camps involved and you can read many articles on
Lothar von Trotha, mainarchitect of this. Germany was justifying breach of Geneva Convention on the fact that Geneva Convention did not apply to Hereros as they were "subhuman". However Germany should not be singled out. This type of reasoning was very widespread in Europe in that time.