Racism was deeply embedded in European belief at the time - both the belief in the inferiority of Africans and the belief in slavery itself.
Europeans believed they were superior to Africans. To their minds this was shown by the slaves':
Beyond that is the human psychological need to believe in self-image, importance and status.
Slaves were often banned from learning to read, earning wages, selling produce or owning wealth. Slaves would be less easy to control if they learnt to organise themselves, communicate, develop unsupervised movement about the country, or develop ambitions and relationships. There were unsuccessful attempts to discourage mixed-race sexual relationships, for instance by regulating that any children born as a result would be slaves.
Other controls were designed to maintain distinctions between the enslaved and the free, between Africans and Europeans. Use of language such as 'Negroes' (black Africans) and 'Servants' (poor white Europeans) started to emerge in legal codes, regardless of slave status.
Is one half of the human species, like the poor African enslaved people, to be subject to prejudices that brutalise them only to sweeten the cup of me?Mary Wollstonecraft