much of the slavery in the arab slave trade had to do with the fact that the africans were dar al harb and without a written language were considered barbarians. and since they couldn't go much further than western india, and they could never hope to take europe over again, they were easy targets. the entirety of west africa's islamification torpedoes your argument that racism began with the arab slave trade, for example.
in fact, there were quite a few edicts issued in regards to ARABS and other muslims being sold into slavery and taken to the east indies and whatnot. shit, the entire suwarian tradition stressed co-existence between muslims and all people, and he was an incredibly influential scholar.