"The killing in Darfur, a vast region in western Sudan, is not a case of religious persecution, since the killers as well as the victims of this genocide are Muslim."
It's rather like saying the killing of the Huguenots was not a case of religious persecution, since the killers as well as the victims of that genocide were Christian.
Some reports from a couple of years ago indicated four traits that usually co-occurred: Arabic/strict+traditional Islam/slightly lighter skin on average/nomadic ~ non-Arabic-speaking/laxer Islam/dark skin/settled. I.e., there was a religious component: takfir is not unheard of. Other reports pointed out that while a Janjaweed may say 'black', the man wielding the epithet could be just as dark as the 'black' man was: the epithet wasn't just, or even primarily, racial. After all, there is nothing that can be called an 'Arab' race at this point, it's mostly a cultural and linguistic term. It would be of interest to see if the co-occurrence of the four traits really did hold.
Then there's this:
http://www.nytimes.com/reuters/international/international-africa-summit.html