Capitalism needs always growing and expanding markets in order to keep giving the owners of capital with surplus value; therefore, it colonized inhabited lands to tap on new markets and uses the population of over exploited countries as slave labor for maximum profits. It uses race and racism as a convenient story to justify why the slaves are in the position of slaves and why the native people were genocided to take their land. This is why imperialism is the highest stage of capitalism and racism is a tool of capitalism. To learn more about this please read