I don't feel guilty about anything here, frankly. I didn't enslave anyone, and neither did my family.
That doesn't mean I have to feel comfortable being reminded of something that was wrong and still has effects on our lives today, especially if I'm being reminded of it by a game like RE.
I agree that it shouldn't make a difference whether it's a black or a white zombie. Actually, it wouldn't if you had black AND white zombies. But IMHO we're simply not at that point yet where it truly doesn't make a difference, no matter what the combination or setup. Or maybe, for better or worse, some people are.
Enjoy the game.