Answer:
Entrenched racism among Europeans meant that slavery took on a racial tone. Ideas of racial differences made it easier to justify slavery. The enslavement of Africans was justified by the belief that Africans were inferior to Europeans.
Several ideas from the time supported the enslavement of Africans:
Africans were seen as more suited to work on the plantations
African captives would be executed if the slave trade was abolished
African slaves were seen as benefitting from being looked after by the superior Europeans