What race ARE Egyptians, if not caucasian?
There's certainly no such thing as an Arab race. If the skeletons of Osama Bin Laden and Saddam Hussein were found in central Park, they'd be described as the skeletons of two "middle-aged caucasian men."
Up thread people were mocking the idea of a Lebanese being described as "white." Well, are Israelis white? You'd be hard pressed to tell a Lebanese from an Israeli physically, and the Israeli is going to be just as swarthy, perhaps even more so.
The only real thing with anything resembling a scientific or genetic basis would be to describe someone as "Mediterranean" - but that includes Sicilians, Greeks, Tunisians, Lebanese, Spaniards, etc.
Bottom line is people WANT to define Arabs and/or Muslims as some completely distinct "other" when it's not true on a biological or genetic basis.
And of course we have the irony of the Tsarnaevs who are LITERALLY "Caucasians."