Oh yeah.."There is no superiority for an Arab over a non-Arab, nor for a non-Arab over an Arab. Neither is the white superior over the black, nor is the black superior over the white -except by piety."
- Prophet Muhammad (s)
Notice: He (s) didn't even say "except by religion", but said "except by piety", which rests in the heart and only God can judge and see.
Lets speak about muslim slave trade then