If i'm totally honest i would choose to save the black freind over a white stranger. So that significantly weakens my argument.
But i still think i make a good point that people feel loyalty to people in order to genetic similarity. That is why in ancient times people were first loyal to their family, then their clan (extended family), then clans similar to their own and finally people unrelated.
I did say in my post "with all things being roughly equal". I.e if everyone in the room was a stranger i would probably choose the white man over the black man.
My point is that race would factor into that situation, as a determinating factor if both were strangers. I think many people would do the same.