Is the Gerald Horne book out? He's a great writer, and I will check Marozzi's book out.
Generally speaking, I think a lot of Black ppl overlook Arab slavery because they don't know about it, and there have been a lot of popular Black Muslims like Muhammad Ali & the NOI.
From what I recall, if you press them they will say "the original Arabs were Black, so Arabic is a Black language". Regardless if that is true, it doesn't erase the anti-Black slave trade and racism from non-Black Arabs.
It's a very important topic and needs more discussion and awareness.