From the moment the first Europeans discovered the continent of Africa, they began to raid it. They also introduced the appalling, degrading and brutal practice of slavery (most captured Africans were forcibly taken - sometimes with the self-serving collusion of other Africans and Arabs - to America and the Caribbean islands). The long conflict between persecuted Blacks and prejudiced, powerful Whites had begun. (Namibia's neighbour is South Africa, which for decades brutally imposed a strict apartheid segregation system.)
After slaves, land: without any consideration for existing populations, white colonists helped themselves to vast tracts of Africa and the riches many contained. Africa's 20th century history has to be seen in the light of this cavalier treatment. When the colonies became economic burdens to the colonising countries, they were abandoned, leaving the Africans to cope as best they could. Later many African states became the site for 'proxy wars' : the USA and the former Soviet Union armed and trained Africans to fight on opposing sides in internal disputes. When the Cold War ended, the armaments remained in the hands of Africans seeking independence or power. Millions of Africans have died in war, massacres and genocide, taught to them by the West.
The impulse to enslave is one that has, too often, been observed in many small-scale human situations: marriage, the workplace, the school playground. That's where it is first experienced and encountered, and where it needs to be stopped.
Empire-building in Africa and Asia reached its peak in the 19th century, and the 20th century has seen the often violent results of empires being dismantled. Grievances, injustice, poverty are the inheritance of poor countries and peoples, and the roots of war and genocide. Empire-building of another kind continues, in the form of multinational corporations and globalisation, which themselves involve injustice, oppression and slave labour: more grievances leading to conflict.
A kind of empire-building on a small scale happens in communities, workplaces and businesses. It reinforces a grasping, ruthless attitude that fails to respect individuals who 'get in the way'. Its dangers need to be recognised.