Ignorance is such a hurtful word.
I understand your point and lets rephrase it. Lets call it lack of socialization.
When a dog is not around other dogs and different people it can develop behavioral problems. Socializing the dog helps reduce those problems.
If it works in dogs, why not in humans?
Was there even a control group in this study? All it said was that essentially, babies prefer people of their own race. Wow not surprising given that they mostly are around people of their own race (the parents or other family) for like 90% of the time.
What they need are a control group and then a group of babies who spend equal amounts of time over their short life spans with different races. Then, perform the same experiment.
If you were wandering in the forest and came on a creature you never saw before, would you not initially be timid of it and prefer to be around creatures you knew? Until you found otu what this new creature was and how it behaved, you would most likely have a negative bias toward preferring to be near it.