So lets assume the real Hebrews were black for a second. What is supposed to be the big deal about Hebrews to begin with?
Are they supposed to be god's chosen people? If that's the case....... 
This is exactly it. It all comes down to being "chosen" in Gods eye. If you reject the idea of a existence of a God, then who really cares who the first Hebrews were.
Its all about, "God loves my people more than your people, therefore I am chosen and special." But if you reject God, then it doesn't make a world of difference who was first, second or third, since we will all wind up in the same place: 6 feel below the ground.