Actually most of the mixture was between Berber/Arab males and European females. Most of the slaves taken into Northwest Africa were Slavic woman from Eastern Europe, which is where the word slave comes from. Also most people seem to differentiate Berbers from blacks, when Berbers are not one homogeneous people and there were black back then and there are still black Berbers around. If all Africans are considered non Muslim, then Berbers are non Muslim since they are African. And Africans were not all considered non Muslim since people like Mansa Musa back then was considered Muslim and was highly respected.
Yes Arabs did have black slaves. But Arabs enslaving blacks is highly exaggerated. African slaves back then during the medieval period were not even on the top list(Europeans were) and the Trans Sahara trade(which North Africa was a part) mostly imported European slaves. Arabs only brought slaves from the Swahili coast from Muslim Africans. Most Africans slaves ended up in Arabia, not North Africa. Like I said modern day North Africans are the result of African men and European women, and as result almost all are mixed. North Africans Y-DNA even makes things clearer since they carry African E-M81 around 80%.
So no. Arab/Berber men did not take African women, it was actually African men taking European women based off the Y-DNA frequencies above...