The ONLY nationality given any sort of preference is UAE nationals, for the obvious reason that they'd like as many of their own citizens flying their aeroplanes - and the UAE is by no means alone in having that preference.
Judging by the extraordinary racial/nationality mix you see on the flight deck, there would appear to be no policy in place to avoid any race or nationality - I'm assuming, (pretty safely, I'd say) - with one expeption when it comes to nationality, and that's towards citizens of that State-that-can't-be-named, the 'hard place' King Abdullah of Jordan was referring to when he said that his country was "between Iraq and a Hard Place". That avoidance doesn't extend to people whose religion is the main religion of that 'hard place', for there are a number of pilots in the airline of that religion, and I know one or two of them make no attempt to hide their religion.
The only other 'skew' that I'm aware of is a desire not to have too large a group of any one particular nationality. As for why they want that, I'll leave for someone else to answer.