sadly many of our young black men and women think like this. its a subconscious reflection of their own personal dislike. its more than "i dont want a dark baby" its basically saying i dont want a baby that looks like my black ugly ass.
and at that point any white girl, no matter fat as hell, or skinny and ugly as hell is off limits, because a baby by them still equals looking "better than my black ugly ass"
you should want your children to be a reflection of yourself. but in this society where everything black is still bad, and kids are in school being called skillet, too black, i was once with a girl who family literally called her "smut" for how dark she is, then they choose lighter in hopes their child dont endure the same hatred that developed the self hatred they fight with today.