Yes, I agree. But the "Arab" versus "Ethnically Black" dichotomy that many people are trying to use to specify the differences between the two groups is a false dichotomy, since both groups are ethnically Black. The term "Arab" in this context most probably refers to language, and that is probably what makes the "Arabs" and "non-Arabs" in this context different ethnicities. But it's definitely not a conflict between "Blacks" and "non-Blacks".